427 L92 a4 GTO issue

[10secvette]

I need some help.

I put together a 427 L92 for my 2005 GTO. It was tuned and put down 490 rwhp unlocked through a ss3600 tc. The car ran fine for a week. I took it to the track and ran a 11.60@ 120 on the first pass. I let the car cool down a touch and on the second pass it layed down a 12.55 @105. It had a rough idle while driving back to the pits. The car left hard but layed down at 1/2 track. While looking the car over in the pits, I discovered a hanging ground wire off the drv. side head. I figured I had found the problem. Put the ground back on and no improvement. At this point the car would hardly idle, and was backfiring throught the intake. We towed it home and here we are today.

I have changed or tested all the sensors, changed plugs, plug wires, coil packs, throttle bodies, intakes, etc. At this point it's idling again, but when in gear with the traction control on, while steeping on the brake pedal, the pcm pulls timing to -3 to -5 degrees almost stalling the engine. It only does this while in gear and with te traction control on. With traction control off, the car is fine so to speak. It lacks power, but I think a retune is in order.

While driving to day, it was o.k. with the tc off, but towards the end of my 15 mionute ride, it was loading up and poppping through the intake agin. I am stumped.

Tune and log available to email. I have no clue how to attach.

[joecar]

Is it now always backfiring thru the intake...?

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[10secvette]

Is it now always backfiring thru the intake...?

To attach files:
- start a reply and press the button "Go Advanced",
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Not always. It started to pop out the intake towards the end of my drive/scan.When this initially started, it popped out the intake like there was a vac.leak. I scaned it and saw the pcm pulling timing, I bumped the timimg and got rid of the popping.

Thanks!!

[joecar]

Verify:
- scan for DTC's... address these first;
- not overheating.
- no vacuum leaks.
- check that injectors are not leaking (check rail pressure with engine off, should hold steady for 1 or 2 minutes).

[joecar]

Backfire

Checks
Actions
DEFINITION : The fuel ignites in the intake manifold or in the exhaust system, making a loud popping noise.
Preliminary Checks


Refer to Important Preliminary Checks Before Starting in Symptoms - Engine Controls (http://127.0.0.1:9001/servlets/CellHandler?CellId=32902&RefDoc=682705) .
Search for bulletins.
Inspect the powertrain control module (PCM) grounds. Ensure that they are clean, tight and in the proper locations. Refer to Engine Controls Schematics (http://127.0.0.1:9001/servlets/CellHandler?CellId=31947&RefDoc=682705) .

Fuel System


Test for incorrect fuel pressure. Refer to Fuel System Diagnosis (http://127.0.0.1:9001/servlets/CellHandler?CellId=31918&RefDoc=682705) .
Test for a restricted fuel filter. Refer to Fuel System Diagnosis (http://127.0.0.1:9001/servlets/CellHandler?CellId=31918&RefDoc=682705) .
Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (http://127.0.0.1:9001/servlets/CellHandler?CellId=32631&RefDoc=682705) .
Inspect that each injector harness is connected to the correct injector/cylinder according to the firing order. The firing order is : 1-8-7-2-6-5-4-3. Relocate the injector harnesses as necessary.

Sensor/System


Test the Secondary Air Injection (AIR) system. Refer to DTC P0410 (http://127.0.0.1:9001/servlets/CellHandler?CellId=32831&RefDoc=682705) .
Inspect the air intake system and crankcase for air leaks.
Test the crankcase ventilation valve for proper operation. Place a finger over the inlet hole in the valve end several times. The valve should snap back. If not, replace the valve.
Verify proper calibration of speedometer. Connect Signal Generator J 33431-B (http://127.0.0.1:9001/servlets/RetrieveTif?pic=9194) to VSS electrical connector. Ignition ON, tester ON and monitor the speedometer. The speedometer should indicate 86 km/h (54 mph). Refer to Diagnostic System Check - Instrument Cluster (http://127.0.0.1:9001/servlets/CellHandler?CellId=50521&RefDoc=682705) in Instrument Panel, Gauges and Console.
Use a scan tool in order to monitor the KS system for excessive spark retard activity. Refer to Knock Sensor (KS) System Description (http://127.0.0.1:9001/servlets/CellHandler?CellId=32897&RefDoc=682705) .

Ignition System


Test for proper ignition voltage output with spark tester J 26792 (http://127.0.0.1:9001/servlets/RetrieveTif?pic=5381) . Refer to Electronic Ignition (EI) System Diagnosis (http://127.0.0.1:9001/servlets/CellHandler?CellId=32032&RefDoc=682705) .
Inspect for an intermittent ignition system malfunction in the following circuits:

Ignition control circuit
Power and ground to the ignition coils

Remove spark plugs and inspect for the following:

Wet plugs
Cracks
Wear
Improper gap
Burned electrodes
Heavy deposits Refer to Spark Plug Inspection (http://127.0.0.1:9001/servlets/CellHandler?CellId=32894&RefDoc=682705) .




An improper spark plug gap causes a driveability condition. Gap the spark plugs using a wire gauge gap tool. Refer to Spark Plug Replacement (http://127.0.0.1:9001/servlets/CellHandler?CellId=32530&RefDoc=682705) .
Determine the cause of the fouling before replacing the spark plugs. If the spark plugs are gas fouled, refer to DTC P0172 or P0175 (http://127.0.0.1:9001/servlets/CellHandler?CellId=32908&RefDoc=682705) . If the spark plugs are coolant fouled or oil fouled, refer to Oil Consumption Diagnosis (http://127.0.0.1:9001/servlets/CellHandler?CellId=44509&RefDoc=682705) in Engine Mechanical-5.7L or Loss of Coolant (http://127.0.0.1:9001/servlets/CellHandler?CellId=37222&RefDoc=682705) in Engine Cooling.
Inspect the secondary ignition for the following conditions:

Ignition wires arcing to ground
Ignition coils arcing to ground

Wet the secondary ignition system with water from a spray bottle. Wetting the secondary ignition system may help to locate damaged or deteriorated components. When you apply the water, look and listen for arcing or misfiring.
Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) System Diagnosis (http://127.0.0.1:9001/servlets/CellHandler?CellId=32032&RefDoc=682705) .

Engine Cooling System


Inspect the engine coolant level for being low. Refer to Draining and Filling Cooling System (http://127.0.0.1:9001/servlets/CellHandler?CellId=37226&RefDoc=682705) in Engine Cooling.
Test the engine thermostat for proper operation and heat range. Refer to Thermostat Diagnosis (http://127.0.0.1:9001/servlets/CellHandler?CellId=37167&RefDoc=682705) in Engine Cooling.

Engine Mechanical


Inspect engine mechanical for the following:

Test the engine compression. Refer to Engine Compression Test (http://127.0.0.1:9001/servlets/CellHandler?CellId=44391&RefDoc=682705) in Engine Mechanical-5.7L.
Sticking or leaking valves
Worn camshaft lobes
Valve timing
Bent push rods
Worn rocker arms
Broken valve springs
Excessive oil in combustion chamber due to leaking valve seals. Refer to Oil Consumption Diagnosis (http://127.0.0.1:9001/servlets/CellHandler?CellId=44509&RefDoc=682705) in Engine Mechanical-5.7L.

Inspect for incorrect basic engine parts. Inspect the following components:

The camshaft
The cylinder heads
The pistons


Additional Checks


Inspect the vacuum hoses for splits, for kinks, for and proper connections and routing as shown on the Vehicle Emission Control Information label.
Inspect the intake manifold and the exhaust manifold passages for casting flash. Refer to Exhaust Manifold Cleaning and Inspection (http://127.0.0.1:9001/servlets/CellHandler?CellId=44489&RefDoc=682705) and Intake Manifold Cleaning and Inspection (http://127.0.0.1:9001/servlets/CellHandler?CellId=44488&RefDoc=682705) in Engine Mechanical-5.7L.
Test the Transmission Torque Converter Clutch (TCC) operation. The scan tool should indicate an RPM drop when the TCC is commanded ON. Refer to Diagnostic Starting Point - Automatic Transmission (http://127.0.0.1:9001/servlets/CellHandler?CellId=7020&RefDoc=682705) in Automatic Transmission-4L60-E.
Inspect the exhaust system for possible restrictions. Inspect the following components:

Inspect the exhaust system for damaged or collapsed pipes. Refer to Restricted Exhaust (http://127.0.0.1:9001/servlets/CellHandler?CellId=62242&RefDoc=682705) in Engine Exhaust.
Inspect the exhaust manifold for a collapsed inner wall. Refer to Exhaust Manifold Cleaning and Inspection (http://127.0.0.1:9001/servlets/CellHandler?CellId=44489&RefDoc=682705) in Engine Exhaust.
Inspect the mufflers for heat distress or possible internal failure. Refer to Symptoms - Engine Exhaust (http://127.0.0.1:9001/servlets/CellHandler?CellId=37994&RefDoc=682705) in Engine Exhaust.
Inspect for a possible plugged 3-way catalytic converters by comparing the exhaust system back pressure on each side of the engine. Test the back pressure by removing the AIR check valves near the exhaust manifolds or the Heated Oxygen sensors. Refer to Restricted Exhaust (http://127.0.0.1:9001/servlets/CellHandler?CellId=62242&RefDoc=682705) in Engine Exhaust.

Electromagnetic Interference (EMI) on the reference circuit can cause an engine miss condition. A scan tool can usually detect EMI by monitoring the engine RPM. A sudden increase in the RPM, with little change in actual engine RPM change may indicate that EMI is present. Inspect for high voltage components near the ignition control circuits if a condition exists.
Test the PNP switch circuit. Refer to Park/Neutral Position Switch Adjustment (http://127.0.0.1:9001/servlets/CellHandler?CellId=6964&RefDoc=682705) in Automatic Transmission-4L60-E.
Inspect for faulty engine mounts. Refer to Engine Mount Inspection (http://127.0.0.1:9001/servlets/CellHandler?CellId=44460&RefDoc=682705) in Engine Mechanical-5.7L.

[joecar]

Do you have cats...? Measure exhaust back pressure at front O2 bungs.

Check plug wires for crossfire... not really possible unless you have long plug wires.

[ssvolvo]

At this point I think the thing to do is start with the actual engine; and performing a leakdown test is in order. A basic leakdown tester is available through Summit pretty cheap. I find a leakdown test much more accurate and telling of "small" problems internally that a compression cranking test just seems to skip over.

Before you chase your tail anymore...check the bare bones basics.

Your high and low spark tables are identical, so knock retard is essentially disabled. Do you have a log of the 11.60 run?

Good luck, John

[10secvette]

At this point I think the thing to do is start with the actual engine; and performing a leakdown test is in order. A basic leakdown tester is available through Summit pretty cheap. I find a leakdown test much more accurate and telling of "small" problems internally that a compression cranking test just seems to skip over.

Before you chase your tail anymore...check the bare bones basics.

Your high and low spark tables are identical, so knock retard is essentially disabled. Do you have a log of the 11.60 run?

Good luck, John

I thought I logged the runs, but apparently brushed the touchpad and stopped the logs.:angel_innocent:

I did a leakdown and compr. test last week. No problems mechanically. Fuel pressure was checked, ok.

No cats.

The main point is that with TC on, while in gear and stepping on the brakes, the pcm starts to pull timing and damn near stalls the engine. It only does this with TC on. Timing goes to about -5'. I have no clue.........

[ssvolvo]

You might try to zero the table in B5136. How about B9902 TCS patch if you are running MAFless?

Also it seems that your C0805 is out of range.

I don't understand some of the changes in C0803,4,5,6. But I don't have a lot of experience in this area. Maybe some of the fly by wire techies can enlighten us.

Did you take the wide band out already? You could use a bit of work on the VE B0200.

Cheers, John

[DrkPhx]

First I would mention the car runs very hot; too hot. Second, are you sure all of the grounds are properly tightened? Besides the low timing at idle (-10.0 at times) and cruise (5.0 at hwy speed), there are times when some of the PIDS flat line which almost would seem there is no signal (or very weak) coming from the sensors causing erroneous readings. I would also check the battery voltage and alternator output under load.

[10secvette]

First I would mention the car runs very hot; too hot. Second, are you sure all of the grounds are properly tightened? Besides the low timing at idle (-10.0 at times) and cruise (5.0 at hwy speed), there are times when some of the PIDS flat line which almost would seem there is no signal (or very weak) coming from the sensors causing erroneous readings. I would also check the battery voltage and alternator output under load.


I agree, the car ran hotter than normal. The -10' of timimng only shows up when TC is off, in gear and on the brakes. I just watched the scan from start to finish, I did not see the pids flatline until the engine was shut down towards the end and I left the scanner on. I just checked all of the grounds per memory and the shop manual. All are secure and tight. I did another leakdown today. All cyliners are at 10% or below. I'm borrowing a Tech2 on Monday and see what the hell is happening with some of the other modules.

[joecar]

Some ideas:
- log the pids whose names start with EST_ (electronic spark timing).
- look at some tables like B5105, B5107.

[DrkPhx]

Sorry I should be more specific. Whenever the timing drops to -10 at idle and 5 at cruising speed, both O2's show 0.00v. It may be nothing, but I've never seen that before.

[10secvette]

Sorry I should be more specific. Whenever the timing drops to -10 at idle and 5 at cruising speed, both O2's show 0.00v. It may be nothing, but I've never seen that before.


Cool, thanks!!

[DrkPhx]

The -10' of timimng only shows up when TC is off, in gear and on the brakes.

But what about when it suddenly drops to 5.0 degrees at hwy speed at frames 8942-9002 and again from 14159-14203? Oddly enough the timing jumps up to 39-40 degrees then drops to 5.0.

[10secvette]

But what about when it suddenly drops to 5.0 degrees at hwy speed at frames 8942-9002 and again from 14159-14203? Oddly enough the timing jumps up to 39-40 degrees then drops to 5.0.

New ecm should be here anyday. The tune has been reviewed by a few people and nobody has been able to find anything screwy with it. It's been tech2'd and no codes or anything showing up malfunctioning. I'm lost, so I ordered a new ecm to start eliminating things. Wish me luck.

[DrkPhx]

New ecm should be here anyday. The tune has been reviewed by a few people and nobody has been able to find anything screwy with it. It's been tech2'd and no codes or anything showing up malfunctioning. I'm lost, so I ordered a new ecm to start eliminating things. Wish me luck.

Rarely is a new ECM needed, but you never know it could be the problem. I would try a full reprogram (not just a flash) of the old ECM before you swap computers as a last ditch effort. Keep us posted.

[10secvette]

Rarely is a new ECM needed, but you never know it could be the problem. I would try a full reprogram (not just a flash) of the old ECM before you swap computers as a last ditch effort. Keep us posted.


Thanks, that was tried early on. I hate to just start throwing parts at it, but it's been two months and I need to do something to try and fix this lump in my garage.

[Stealth97]

You checked compression and leakdown in all 8 holes?

Compression tells you if a ring is fried. Leakdown tells you if valves are fried or not opening/closing

This is a new motor, right? Is it possible a valvespring broke? I'd pull the valve covers just to give it a look see. Easy thing to do (well, on my truck anyway).

I'm wondering why it layed down at half track. Layed down on a shift too I assume? Overrevved?

Is it possible that a valve came in contact with a piston at high RPM (valve float) and now all your valves are bent, leading to no compression?

Just trying to be of assistance. May not be EFI related, but hard parts related.

Please let us know what you find! I am very very interested to know.

Eric / Stealth

[10secvette]

You checked compression and leakdown in all 8 holes?

Compression tells you if a ring is fried. Leakdown tells you if valves are fried or not opening/closing

This is a new motor, right? Is it possible a valvespring broke? I'd pull the valve covers just to give it a look see. Easy thing to do (well, on my truck anyway).

I'm wondering why it layed down at half track. Layed down on a shift too I assume? Overrevved?

Is it possible that a valve came in contact with a piston at high RPM (valve float) and now all your valves are bent, leading to no compression?

Just trying to be of assistance. May not be EFI related, but hard parts related.

Please let us know what you find! I am very very interested to know.

Eric / Stealth


It's not mechanical, all of the above checked and ruled out.

[Stealth97]

You checked compression and leakdown in all 8 holes?

Compression tells you if a ring is fried. Leakdown tells you if valves are fried or not opening/closing.

This is a new motor, right? Is it possible a valvespring broke? I'd pull the valve covers just to give it a look see. Easy thing to do (well, on my truck anyway).

I'm wondering why it layed down at half track. Layed down on a shift too I assume? Overrevved? Did you hit 2nd instead of fourth and hit 8000 RPM?

Is it possible that a valve came in contact with a piston at high RPM (valve float) and now all your valves are bent, leading to no compression? You may not float the valves normally but you could float them on a mis-shift. I have also seen this happen. Your setup is extreme (427) so I'd imagine the least room for error.

Just trying to be of assistance. May not be EFI related, but hard parts related.

Please let us know what you find! I am very very interested to know.

Car has no catalytic converters right? Maybe a high EGT melted the substrate inside the cat into a ball. The ball is now blocking your exhaust. Happened to me before.

Eric / Stealth

[joecar]

If it was good (1st pass: 11.60@ 120) and then in a short time it was no good (2nd pass: 12.55 @105, "layed down at 1/2 track"), then something broke/bent...

Have you considered any of these:
- timing chain jumping,
- pushrods, rockers, springs, lifters, cam, valve (as Eric/Stealth said),
- cam walking,
- CKP reluctor hitting/bending,
- CKP and/or CMP sensor failure,
- other sensor failure,
- air leak in intake/exhaust,
- blockage in exhaust.

Are you running MAF or MAF-less (your MAF pid is all zero)...?

And set C0805 to an in-range value (altho I don't think that's it).

[10secvette]

While looking the car over in the pits, I discovered a hanging ground wire off the drv. side head. I figured I had found the problem. Put the ground back on and no improvement. At this point the car would hardly idle, and was backfiring throught the intake.


I think this may have fried the ecm.

The front of the motor came off, no timing chain issue. CPS was changed along with all of the other engine sensors. Microscope was used to check the reluctor, ok. No vac. leaks. No cats on the car at the track. No maf.

[Stealth97]

If it was good (1st pass: 11.60@ 120) and then in a short time it was no good (2nd pass: 12.55 @105, "layed down at 1/2 track"), then something broke/bent...

Have you considered any of these:
- timing chain jumping,
- pushrods, rockers, springs, lifters, cam, valve (as Eric/Stealth said),
- cam walking,
- CKP reluctor hitting/bending,
- CKP and/or CMP sensor failure,
- other sensor failure,
- air leak in intake/exhaust,
- blockage in exhaust.

Are you running MAF or MAF-less (your MAF pid is all zero)...?

And set C0805 to an in-range value (altho I don't think that's it).

Agreed. I was just coming back to say is it possible the timing chain jumped a tooth or something?

No DTC's? Do you have a MIL malfunction indicator light? I'd check for DTC's also.

Quite possibly is the intake manifold leaking somehow (you say it backfired, did it break. Is it a sheet metal intake? One N20 explosion and it breaks at the welds. Repair it?). I know you aren't nitrous but any backfire of pressure could possibly break it.

Throwing out ideas trying to help. Lets get this thing fixed!

[Stealth97]

I think this may have fried the ecm.

The front of the motor came off, no timing chain issue. CPS was changed along with all of the other engine sensors. Microscope was used to check the reluctor, ok. No vac. leaks. No cats on the car at the track. No maf.

What state are you in? If you lived near me you could borrow my spare ECM. I live near joecar in Los Angeles, CA.

[10secvette]

Agreed. I was just coming back to say is it possible the timing chain jumped a tooth or something?

No DTC's? Do you have a MIL malfunction indicator light? I'd check for DTC's also.

Quite possibly is the intake manifold leaking somehow (you say it backfired, did it break. Is it a sheet metal intake? One N20 explosion and it breaks at the welds. Repair it?). I know you aren't nitrous but any backfire of pressure could possibly break it.

Throwing out ideas trying to help. Lets get this thing fixed!

No dtc's.
I borrowed a tech 2 and scanned everything, nothing tripped. I swapped intakes, no change. I appreciate the idea's. I think I've gone through or swapped about everything I could think of besides the major control modules. It's frustrating because I've been messing around with LSx motors for 10 years now and this one has me stumped.

[10secvette]

What state are you in? If you lived near me you could borrow my spare ECM. I live near joecar in Los Angeles, CA.

Damn, I'm in Murrieta, near Temecula. I'm in and out of LA every week. I appreciate the offer, I would have taken you up on it but my new one should be hear Monday or Tuesday.

I will say this, if the ecm is not the issue, I have plenty of beer in the fridge about 20 inches from the nose of the car for whoever wants to come over and troubleshoot with me.:grin:

[joecar]

Murrieta... I'll have to ask my Mrs for permission... :D

[10secvette]

Murrieta... I'll have to ask my Mrs for permission... :D


Bring her along, she can go wine tasting or shopping w/my wife. :cheers:

[joecar]

She'll want to go to the casino...:bawl:

I'll check my GM service manual for 2005 GTO.

[Stealth97]

Damn, I'm in Murrieta, near Temecula. I'm in and out of LA every week. I appreciate the offer, I would have taken you up on it but my new one should be hear Monday or Tuesday.

I will say this, if the ecm is not the issue, I have plenty of beer in the fridge about 20 inches from the nose of the car for whoever wants to come over and troubleshoot with me.:grin:

Temecula ain't far (2-3 hrs max). How did I figure you were in Cali? LOL.

You, joecar and myself should all meet up sometime. We can show our rides and chat a bit.

Eric

[Stealth97]

Bring her along, she can go wine tasting or shopping w/my wife. :cheers:

I'm not married yet but I have a very serious girlfriend. Maybe your wives can knock some sense into mine for me? I sure as hell can't seem to do it. :bangin:

[joecar]

Yeah we should meet up sometimes... :cheers:

we usually stop at the Walgreens on California Oaks Rd just off I-15 on our way to Pala (she's gotta pee on a 80 minute trip... :nixweiss:).

[joecar]

I'm not married yet but I have a very serious girlfriend. Maybe your wives can knock some sense into mine for me? I sure as hell can't seem to do it. :bangin:Lol... it won't work... they'll just gang up against us... :doh2::doh2::doh2:

[10secvette]

Yeah we should meet up sometimes... :cheers:

we usually stop at the Walgreens on California Oaks Rd just off I-15 on our way to Pala (she's gotta pee on a 80 minute trip... :nixweiss:).

Sounds good. I'm about 5 minutes away from the Walgreens. Next time call.....:hihi:

[10secvette]

Lol... it won't work... they'll just gang up against us... :doh2::doh2::doh2:


Yeah that. Best laid plans....... we will end up paying for it in the end that's for sure.

[joecar]

Lack of power:

Might also consider these:
- pressure test coolant system hot (as hot as it will go),
- use "block test kit" (checks for blowby gases in coolant sample),
Some leaks are so small they don't show up with compression/leakdown tests.

Do you have access to an oscilloscope...?
If so check the voltage signal from the CKP sensor for uniformity
(watchout, most scopes have common ground across all channels).

Did anything get sucked into intake manifold that is restricting a port.

Does each spark plug make a big spark when using the spark tester
(looks like a spark plug with no ground electrode and with a ground clamp)...?


Traction control pulling timing:

Also, I re-read what you said about traction control... might check:
- ABS wheel reluctors (see if you get AC voltage on DMM, or use oscilloscope),
- wiring for ABS wheel sensors,
- connections/power/ground to ABS (service manual calls it EBCM) module,
- are there any ABS/BCM DTC's...?

[427]

okay-what about when you put load on the engine it turns to shit-

maybe the reg wheel on the crank is a bit loose when on load-

i keep seeing these reg wheels as small problems lately--

[joecar]

The CKP wheel is very important... if the signal is not 100% then everything goes wrong...

Remove the CKP sensor and slowly turn the crank while eyeaballing the reluctor wheel (might have to remove the starter to do this).

[10secvette]

The CKP wheel is very important... if the signal is not 100% then everything goes wrong...

Remove the CKP sensor and slowly turn the crank while eyeaballing the reluctor wheel (might have to remove the starter to do this).
Agreed, already checked, a ok.

[10secvette]

No love from the USPS again today.

[joecar]

Our 18th wedding anniversary is coming up this weekend... so I'm in a bind (that reminds me I have to go shopping...).

[10secvette]

Our 18th wedding anniversary is coming up this weekend... so I'm in a bind (that reminds me I have to go shopping...).


Congrats!! No worries and no rush. I just went to Albertsons and low and behold there was a small box on the porch. It's here.

If my kids get to bed at a decent hour, it will at least be in and flashed tonight for a early am fire. Fingers crossed!!

[10secvette]

If my kids get to bed at a decent hour, it will at least be in and flashed tonight for a early am fire. Fingers crossed!!

It's in and fired for 1/2 second to confirm it works. Kids rooms are above the garage so until the a.m......

[10secvette]

It's in and fired for 1/2 second to confirm it works. Kids rooms are above the garage so until the a.m......



Back to square one.:bad:

[joecar]

Hmmmm....

I take it that it flashed ok.

Also check the ABS reluctors/sensors on each wheel, and that the ABS/EBCM connecor(s) are good/secure.

[10secvette]

Hmmmm....

I take it that it flashed ok.

Also check the ABS reluctors/sensors on each wheel, and that the ABS/EBCM connecor(s) are good/secure.

Flashed fine, same crap though.

[Stealth97]

Who is the driver of the car? Are you certain it was not overrevved?

Did you ever figure out if maybe a shift was in error and the valves did contact the pistons, slightly bending them, and causing a bad seal on the valve angle mating surface to the head machine work?

Did you check fuel pressure at the rail at idle? What was it? Did you check it under load. Is it possible either you have a plugged filter (unlikely) or a faulty regulator (more likely). Do you have an aftermarket regulator or stock?

Apologies if any of these were discussed/answered. Just throwing out ideas.

Could it be possible that your head gasket failed in between two cylinders? Did you check compression in all 8 holes? I think that would show up on a compression tester but I'm not sure (depending on if the two adjoining cylinders both had some compression at the same time). Again, just throwing out ideas.

Sooner or later we will figure this out.

Did you ever pull the valve covers and look for broken valvesprings? In hi-perf motors people always get real high pressure springs but sometimes those aren't correct. I've heard of quite a few guys with broken valvesprings due to using the wrong part for the wrong application. Seems all too common.

[Stealth97]

Here is another thought. Why not take a stock Corvette tune and load it into the ECM, minus VATS or whatever else you might want/need. Don't go crazy with it, just make it so it will fire up. See if you get a different result with a stock tune. If the car moves under its own power, your tune is FUBAR.

Again, just trying to help. I downloaded a tune out of this guys 96 Chevy truck that was tuned by Ed Wright. Was the most interesting looking tune but it really hauled ass. The one problem was it was burn your eyes rich at idle. You might think your tune is great because it worked for a pass or two, but these ECM's seem much more complicated than we allude to sometimes. I'd try a more stock tune and just see. Can't hurt as long as you don't go full throttle or anything ridiculous.

[10secvette]

Who is the driver of the car? Are you certain it was not overrevved?

Me, a4, no over rev

Did you ever figure out if maybe a shift was in error and the valves did contact the pistons, slightly bending them, and causing a bad seal on the valve angle mating surface to the head machine work?

I can't imagine how it would have happened. I have miles of PTV clearance.

Did you check fuel pressure at the rail at idle? What was it? Did you check it under load. Is it possible either you have a plugged filter (unlikely) or a faulty regulator (more likely). Do you have an aftermarket regulator or stock?

58psi at the rail, stock

Apologies if any of these were discussed/answered. Just throwing out ideas.

Could it be possible that your head gasket failed in between two cylinders? Did you check compression in all 8 holes? I think that would show up on a compression tester but I'm not sure (depending on if the two adjoining cylinders both had some compression at the same time). Again, just throwing out ideas.

As I scan the car, I can see the ecm pulling the timing out as though something is kicking the TC system.

Sooner or later we will figure this out.



Did you ever pull the valve covers and look for broken valvesprings? In hi-perf motors people always get real high pressure springs but sometimes those aren't correct. I've heard of quite a few guys with broken valvesprings due to using the wrong part for the wrong application. Seems all too common.

No broken valve springs.




Ideas are appreciated, it's computer related.

[10secvette]

Here is another thought. Why not take a stock Corvette tune and load it into the ECM, minus VATS or whatever else you might want/need. Don't go crazy with it, just make it so it will fire up. See if you get a different result with a stock tune. If the car moves under its own power, your tune is FUBAR.

Again, just trying to help. I downloaded a tune out of this guys 96 Chevy truck that was tuned by Ed Wright. Was the most interesting looking tune but it really hauled ass. The one problem was it was burn your eyes rich at idle. You might think your tune is great because it worked for a pass or two, but these ECM's seem much more complicated than we allude to sometimes. I'd try a more stock tune and just see. Can't hurt as long as you don't go full throttle or anything ridiculous.


I loaded a stock GTO tune this morning, same thing.

[joecar]

In the scantool, locate the pids that have EST in their name (Electronic Spark Timing)...

One or more of these might indicate the reason who/what/why/where for pulling timing.

(I don't know if all PCM's/ECM's have these pids).

[Stealth97]

Hmm, the ECM keeps removing timing for some unknown reason.

The only thing I can think of is maybe the knock sensor picking up harmonics from your valvetrain (how different than stock is the valvetrain?) and causing the errors. Some aftermarket valvetrains cause harmonics that don't work with stock knock sensors.

Or possibly a pinched wire in between the transmission and the block when you installed the motor. I've heard of this happening on the trucks (seems common, I almost did it to my 97 but caught it on install). Is it possible a wire got pinched?

Is it possible a wire got melted from the headers? Anything close enough to warrant this?

I want to know what is happening and I also want you back down the 1320 so I can see you put this combo to 9.99 @ 129 (wishful thinking for ya!)

[10secvette]

Hmm, the ECM keeps removing timing for some unknown reason.

The only thing I can think of is maybe the knock sensor picking up harmonics from your valvetrain (how different than stock is the valvetrain?) and causing the errors. Some aftermarket valvetrains cause harmonics that don't work with stock knock sensors.

Or possibly a pinched wire in between the transmission and the block when you installed the motor. I've heard of this happening on the trucks (seems common, I almost did it to my 97 but caught it on install). Is it possible a wire got pinched?

Is it possible a wire got melted from the headers? Anything close enough to warrant this?

I want to know what is happening and I also want you back down the 1320 so I can see you put this combo to 9.99 @ 129 (wishful thinking for ya!)


Zero knock shows up. No pinched or melted wires as near as I can tell.

LOL, 11.50 is where it will run, no rollbar for this car.

[shane]

I know you may have checked it but is your reluctor wheel welded to the crank or pressed on? We have seen a couple fail when not welded. Turn over when static but float when running giving wierd timing numbers as the reluctor slips and speeds up.turn the engine over and apply a bit of a load to the reluctor to double check it or get a dual channel trace and check both cam and crank at the same time.
Hope this helps nothing worse than those annoying faults.
Cheers Shane

[gmh308]

Zero knock shows up. No pinched or melted wires as near as I can tell.

LOL, 11.50 is where it will run, no rollbar for this car.

I dont get into this much due to time, but took a look at your log. Two areas where timing is pulled Frame 8930-9011-9100 looks like DFCO/decel retard followed by burst knock retard. There is a common pattern whether moving or stationary.

Hard to tell whether you are on the pedal or not as there is no pedal trace, but the ETC sure looks unstable as it tries to correct idle speed fluctations which may be contributing to BKR levels that hit zero/go negative, or vice versa. Its chasing its tail.

How long had the cam been in the car when you took it to the strip, had a good run went 11.5 and then a lay down run?

Any chance of a dead lifter or cam lobe?

If you go log burst knock + knock on a per cylinder basis, it may point out a particular cylinder that is sick?

On JoeCars point, there are 15 or more timing/knock related PIDS.

Just some ideas man. :) Maybe you covered them all already!

:cheers:

[10secvette]

No time to play but still dead.

[Stealth97]

No time to play but still dead.

Anytime I see an update, I check back. I wish I was more knowledgeable, but even then this problem seems very specific and hard to find.

I'm sure my dad could fix it. He has been a mechanic his whole life. But I wonder how much time it would take for him to figure it out. You have already thrown about every part at it we could think of, and none of that seems to be working.

I'm going to try to ask him about it.

[GNXClone]

Ideas are appreciated, it's computer related.

Maybe something *is* commanding reduced torque? You have the A4, so it could be the TCM. Perhaps traction control as you mentioned. Forgive me if this has been covered, but have you tried disabling the torque reduction tables in the ECM? If that appears to fix it, then you know you're on the right track. And that would explain why a new ECM would still show the problem.

Hate to see a GTO sit idle like that...

[10secvette]

Maybe something *is* commanding reduced torque? You have the A4, so it could be the TCM. Perhaps traction control as you mentioned. Forgive me if this has been covered, but have you tried disabling the torque reduction tables in the ECM? If that appears to fix it, then you know you're on the right track. And that would explain why a new ECM would still show the problem.

Hate to see a GTO sit idle like that...


Update.... after sitting for close to 4 months, I loaded a tune adding timing and raising the idle just to get the car out of the garage. Still no idea what's wrong with this thing. :confused:

[10secvette]

I know you may have checked it but is your reluctor wheel welded to the crank or pressed on? We have seen a couple fail when not welded. Turn over when static but float when running giving wierd timing numbers as the reluctor slips and speeds up.turn the engine over and apply a bit of a load to the reluctor to double check it or get a dual channel trace and check both cam and crank at the same time.
Hope this helps nothing worse than those annoying faults.
Cheers Shane


I believe Shane may be the winner. I'm pulling the engine this week to tear it down and check.

[shane]

No need to pull the engine just pull out the crank sensor out of the block and look in ther if you can, get someone to bar over the engine slowly and push against the reluctor wheel see if it slips...
:cheers:

[10secvette]

No need to pull the engine just pull out the crank sensor out of the block and look in ther if you can, get someone to bar over the engine slowly and push against the reluctor wheel see if it slips...
:cheers:

Will do, I put it on the lift last night. It's not free wheeling, it appears to have "shifted/slipped" on the crank losing it's index. I put a timing light on it yesterday, it's about 13' off actual vs. what's commanded.

BTW, mine was pressed on. I know when they balanced the crank it was removed.

[10secvette]

It's out and the engine is apart. Crank is at the machine shop getting checked. TC is going back to Yank to be restalled. May as well since it's all apart.

[gmh308]

Will do, I put it on the lift last night. It's not free wheeling, it appears to have "shifted/slipped" on the crank losing it's index. I put a timing light on it yesterday, it's about 13' off actual vs. what's commanded.

BTW, mine was pressed on.

I know when they balanced the crank it was removed.


Wonder if they re-installed it using the correct indexing tool, or did it by eye? :shock:

And if they simply cold pressed it on vs heating and shrink fitting it and the shrink fit was stretched.......?

[10secvette]

Wonder if they re-installed it using the correct indexing tool, or did it by eye? :shock:

And if they simply cold pressed it on vs heating and shrink fitting it and the shrink fit was stretched.......?



Machine shop called, around 30' off. Amen we figured it out.

[joecar]

30° off... wow... post pics of the repaired crank.

[10secvette]

30° off... wow... post pics of the repaired crank.

Will do!

Thank you to everyone that shared thier ideas and helping!!!!

[10secvette]

http://img200.imageshack.us/img200/8130/070409171.th.jpg (http://img200.imageshack.us/i/070409171.jpg/)http://img18.imageshack.us/img18/9228/070409168.th.jpg (http://img18.imageshack.us/i/070409168.jpg/)


Re-indexed and tacked on.

Hopefully the wife and kids give me the time to assemble the engine today.

[98 tigershark]

I have a 98 C5 with a L/92 427.
A very nice motor indeed. The overheating problems are familiar to me as well as the lose of power and reduced power and reduced power mode. When you reflash the PCM and it is almost finished, look at the readout at the bottom of the speedo.
See when the tun is done loading if the read out says reduced power mode. If so, you have to re flash the tun until it is gone. THe radiator on my car is to small also. I think the cats also may go over the O2 temp limit of 1279 degrees. These are pretty high performance motors and I think the O2 sensors can be fouled very easy and the cars go into reduced power mode when reflashed quite often. The AIT temp sensor is also very important to move away from these heat creating motors. Loading up is also a constant problem and percolating fuel in the fuel rail also is a constant problem (a return line helps). Another major important issue to watch out for is is to make sure the engine builder or installer made the oil pick up tube adjustment when they installed the pickup tube and windage tray (if you had to drop the windage tray about a half inch the pick up has to be pushed back up that exact amount or else you will hemorrhage oil and it may go into the intake as well. Stock stroke 3.62, new stroke 4.1 so 4.1-3.62=.48in so space the windage tray and then push the pick up up this amount if not done already). These motor also have crank pressure things to watch for so you do not damage the motor. I do think exhaust temp, all cooling issues and breathing issue are important to address prior to the build, as these motors are hungry for air and a good flowing exhaust and a good cooling system. I have had the combo for around a year.
Look into fuel starvation to the motor as according to my math the LS7 injectors are to small for my combo as well as the fuel pump out put (I get fuel starvation at 5,900 rpms in 1st, 5,600 in 2nd, and 5,500 in 3rd.
Also any cooling things for the tranny fluid and oil are equally important
98 tigershark




I need some help.

I put together a 427 L92 for my 2005 GTO. It was tuned and put down 490 rwhp unlocked through a ss3600 tc. The car ran fine for a week. I took it to the track and ran a 11.60@ 120 on the first pass. I let the car cool down a touch and on the second pass it layed down a 12.55 @105. It had a rough idle while driving back to the pits. The car left hard but layed down at 1/2 track. While looking the car over in the pits, I discovered a hanging ground wire off the drv. side head. I figured I had found the problem. Put the ground back on and no improvement. At this point the car would hardly idle, and was backfiring throught the intake. We towed it home and here we are today.

I have changed or tested all the sensors, changed plugs, plug wires, coil packs, throttle bodies, intakes, etc. At this point it's idling again, but when in gear with the traction control on, while steeping on the brake pedal, the pcm pulls timing to -3 to -5 degrees almost stalling the engine. It only does this while in gear and with te traction control on. With traction control off, the car is fine so to speak. It lacks power, but I think a retune is in order.

While driving to day, it was o.k. with the tc off, but towards the end of my 15 mionute ride, it was loading up and poppping through the intake agin. I am stumped.

Tune and log available to email. I have no clue how to attach.

[joecar]

10sv, thanks for the pics.

98ts, thanks for the notes, interesting.

:cheers:

[10secvette]

No problem.

[98 tigershark]

I had a similar symptom as 10secvette. Mine lost timing as well and I was worried it was also the reluctor. Some bad luck with a cracked manifold vacuum fitting in the back and an improperly run vacuum along with crank and valve cover pressure caused the same type of issue were as the timing was not what was commanded. I thought for sure it was a loose reluctor. Thank goodness it was not and I repaired the leaks, re- engineered the PVC system and also made a valve cover breather setup that work great and looks good with the GM performance covers relieving the crank and valve cover pressure. But a vacuum leak did cause allot of problem such as timing was off as to what was commanded, manifold and exhaust backfires overheating, bad fuel economy and weird performance issues. So I also had a cracked vacuum cap in addition to the damaged back of the intake manifold. You could not hear the vacuum leaks as the cam and motor disguised. So I would add vacuum to the list that can cause these symptoms as I thought for sure I had a slipping reluctor and had all the problems mentioned above. So vacuum is very important and my pcm still commanded and logged the right timing but whan checked manualy it was way off from the vacuum leaks.
98tigershark

[gmh308]

http://img200.imageshack.us/img200/8130/070409171.th.jpg (http://img200.imageshack.us/i/070409171.jpg/)http://img18.imageshack.us/img18/9228/070409168.th.jpg (http://img18.imageshack.us/i/070409168.jpg/)


Re-indexed and tacked on.

Hopefully the wife and kids give me the time to assemble the engine today.

30 degrees off! Stunning! When changing reluctors we bake them on a gas burner (similar diameter to reluctor) for a few minutes until they just begin to blue. They drop right on then, finished off with an alignment tool and clamping bolts while they shrink tight. Runout checked to less than 0.020". Never had one move yet. But always a first time. :shock:

[mr.prick]

Welding prevents the possibility of future regrets and you have to wonder
about the engineer that said
"let's install the reluctor and crank pulley with a press fit,
that sh*t will be fool proof". :rippedhand:

[gmh308]

Welding prevents the possibility of future regrets and you have to wonder
about the engineer that said
"let's install the reluctor and crank pulley with a press fit,
that sh*t will be fool proof". :rippedhand:

Sure does!

LOL! Press fit ! That's almost as funny as your Avatar! :hihi:

[10secvette]

Welding prevents the possibility of future regrets and you have to wonder
about the engineer that said
"let's install the reluctor and crank pulley with a press fit,
that sh*t will be fool proof". :rippedhand:

LOL, hence why I pin the crank and now tack the reluctors.

[98 tigershark]

Mine was not the reluctor and I lucked out as the intake vacuum leaks acted as if the motor lost its index. I was wondering if an after the fact weld affects the balancing of the crank assembly? Also a question on cam installation.
I am helping a kid without much money today and he said he installed a new cam and timing chain in his 2000 Camaro. No degree measuring tool for the crank and cam alignment. He also used push rods that are 7.35 and not 7.4 and was told that is OK by a reputable shop. He said he installed the cam the old way (ie #1 cylinder TDC on the compression cycle). I have not seen a new cam and timing chain installed on an LS1 with out the proper tools and references and am wondering if he could really have done this right as he says the car barely runs and I have not helped him yet but would like to go down the list of proper checks today, but the cam thing he has done troubles me. It is Sunday morning July 12 at 10:20 am here and am leaving in about an hour or so to help him but it seems like a mess. Can the cam be installed the way he did it and if so how difficult is it to do right?
98 tigershark



LOL, hence why I pin the crank and now tack the reluctors.

[mr.prick]

How did he check DTC?
I know a lot of people install a cam dot to dot and call it good.

[joecar]

Dot-to-dot may be ok, but requires TDC to be exactly identified (there are maybe 10° of crank rotation at TDC where the piston hardly moves... and what if the cam is ground offset, how will he ever know...? Degree kits are fairly cheap from Jegs or Summit.

The 7.35" pushrods maybe ok if he used the LS7 lifters (which have the PR cup sitting 0.050" higher than the old LS1 lifters).

[10secvette]

Well, the ordeal seems to over for now. Car fired and ran, went for a ride for a few blocks. It needs a bit of idle tweaking, but all in all good. Of course I picked the hottest weekend of the year to stab the motor. LOL.

[98 tigershark]

Hey 10secvette,
Congrats, I hope you like your L92 427 as much as I do mine. I am the baddest nat asp vette in town (We only have 950 people). But I think you will dominate the 11.5 sec class at your track as I have not lost once, even with the bad vacuum leak and all the problems. It is not easy staying above 11.50, as the diff between 11.50 and 11.55 is less than a blink of an eye. Very happy for you. By the way, did anyone find out if the welds on the reluctor have an effect on the crank assembly balance?
98tigershark


Well, the ordeal seems to over for now. Car fired and ran, went for a ride for a few blocks. It needs a bit of idle tweaking, but all in all good. Of course I picked the hottest weekend of the year to stab the motor. LOL.

[10secvette]

Hey 10secvette,
Congrats, I hope you like your L92 427 as much as I do mine. I am the baddest nat asp vette in town (We only have 950 people). But I think you will dominate the 11.5 sec class at your track as I have not lost once, even with the bad vacuum leak and all the problems. It is not easy staying above 11.50, as the diff between 11.50 and 11.55 is less than a blink of an eye. Very happy for you. By the way, did anyone find out if the welds on the reluctor have an effect on the crank assembly balance?
98tigershark


THanks. No, I had them do 3 small tacks, it's so close to the center of the crank it's not going to affect the balance.

[shane]

Just found this thread again, glad you found the problem, guess you owe me a beer(or a ride).
The best thing about these forums is theres always some poor bastard whose been there before you and if your lucky someone will share their info.
Im the first to admit i know enough to get me into trouble and occasionally enough to get me out.
If everyone shares then we can all benefit (or so the theory goes anyway, shame the hptuners forum doesnt work the same, everyones an expert there and not anywhere near as helpful(FORD TUNING ONLY FOR ME ON THERE HONEST).
Welding reluctors should me mandatory on anything that makes good power,
as you now know:doh2:
Cheers Shane

[10secvette]

Just found this thread again, glad you found the problem, guess you owe me a beer(or a ride).
The best thing about these forums is theres always some poor bastard whose been there before you and if your lucky someone will share their info.
Im the first to admit i know enough to get me into trouble and occasionally enough to get me out.
If everyone shares then we can all benefit (or so the theory goes anyway, shame the hptuners forum doesnt work the same, everyones an expert there and not anywhere near as helpful(FORD TUNING ONLY FOR ME ON THERE HONEST).
Welding reluctors should me mandatory on anything that makes good power,
as you now know:doh2:
Cheers Shane

Next time I'm down under the beer is on me!!!:cheers:

[98 tigershark]

I was looking at your collection of larger LS high hp transplants. Impressive!
Out of curiosity,
what are you doing for a fuel pump setup like on the 1999 C5 with the LS7?
I have to upgrade my system this winter. Is there a less expensive way to go about this than the dual in tank setup or out of tank pumps. Or just a system that has worked well for you. I am tired of having to short shift in order to not damage my motor. Thankfully these motors are trq monsters.
You can PM me if you like as that is not the IMO for this thread. I am looking for input for what works well.
Any input would be appreciated. I have a 98 C5 w/ the L92 427 very built.
Thanking you in advance,
98 tigershark

[LM7Tuner]

When you reflash the PCM and it is almost finished, look at the readout at the bottom of the speedo.
See when the tun is done loading if the read out says reduced power mode. If so, you have to re flash the tun until it is gone.

Really? My truck has done this several times before, I assumed it was normal. When it does this I have to reflash the PCM until it doesn't do it?

[10secvette]

I was looking at your collection of larger LS high hp transplants. Impressive!
Out of curiosity,
what are you doing for a fuel pump setup like on the 1999 C5 with the LS7?
I have to upgrade my system this winter. Is there a less expensive way to go about this than the dual in tank setup or out of tank pumps. Or just a system that has worked well for you. I am tired of having to short shift in order to not damage my motor. Thankfully these motors are trq monsters.
You can PM me if you like as that is not the IMO for this thread. I am looking for input for what works well.
Any input would be appreciated. I have a 98 C5 w/ the L92 427 very built.
Thanking you in advance,
98 tigershark

I'm still on the factory fuel system.

[JCA]

I'm havering the same probs with a vx commodore and done every thing and bout to rip the crank out and swap reluctor wheels as I know it was changed on the crank before I brought the stroker kit but reading 98 tiger sharks vaccum leak prob did it shown up crazy map sensor readings it has a fast 102 manifold and big 250degree cam so has high map readings etc now I have tuned in tps ve the timing is all over the place no matter what I do can't hear any vaccum leaks have already pulled manifold and pulled a part and resealed etc problem has been getting worse and worse with time engine will cruise perfect tho