Page 1 of 9 123 ... LastLast
Results 1 to 10 of 89

Thread: 427 L92 a4 GTO issue

  1. #1
    Junior Member
    Join Date
    Jun 2006
    Posts
    41

    Default 427 L92 a4 GTO issue

    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.
    Attached Files Attached Files
    Last edited by 10secvette; January 2nd, 2009 at 10:52 AM.

  2. #2
    Joe (Moderator) joecar's Avatar
    Join Date
    Apr 2003
    Posts
    28,403

    Default

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

    To attach files:
    - start a reply and press the button "Go Advanced",
    - scroll down and press "Manage Attachments",
    - in the Manage Attachments pop up, browse upto 3 files;
    - press upload and wait for it to finish;
    - close the pop up window;
    - finish your reply and submit it.

  3. #3
    Junior Member
    Join Date
    Jun 2006
    Posts
    41

    Default

    Quote Originally Posted by joecar View Post
    Is it now always backfiring thru the intake...?

    To attach files:
    - start a reply and press the button "Go Advanced",
    - scroll down and press "Manage Attachments",
    - in the Manage Attachments pop up, browse upto 3 files;
    - press upload and wait for it to finish;
    - close the pop up window;
    - finish your reply and submit it.


    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!!

  4. #4
    Joe (Moderator) joecar's Avatar
    Join Date
    Apr 2003
    Posts
    28,403

    Default

    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).

  5. #5
    Joe (Moderator) joecar's Avatar
    Join Date
    Apr 2003
    Posts
    28,403

    Default From the service manual

    Backfire

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


    Fuel System

    • Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Test for a restricted fuel filter. Refer to Fuel System Diagnosis .
    • Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • 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 .
    • 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 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 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 .

    Ignition System

    • Test for proper ignition voltage output with spark tester J 26792 . Refer to Electronic Ignition (EI) System Diagnosis .
    • 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:


    • An improper spark plug gap causes a driveability condition. Gap the spark plugs using a wire gauge gap tool. Refer to Spark Plug Replacement .
    • Determine the cause of the fouling before replacing the spark plugs. If the spark plugs are gas fouled, refer to DTC P0172 or P0175 . If the spark plugs are coolant fouled or oil fouled, refer to Oil Consumption Diagnosis in Engine Mechanical-5.7L or Loss of Coolant 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 .

    Engine Cooling System


    Engine Mechanical

    • Inspect engine mechanical for the following:
      • Test the engine compression. Refer to Engine Compression Test 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 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 and Intake Manifold Cleaning and Inspection 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 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 in Engine Exhaust.
      • Inspect the exhaust manifold for a collapsed inner wall. Refer to Exhaust Manifold Cleaning and Inspection in Engine Exhaust.
      • Inspect the mufflers for heat distress or possible internal failure. Refer to Symptoms - Engine Exhaust 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 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 in Automatic Transmission-4L60-E.
    • Inspect for faulty engine mounts. Refer to Engine Mount Inspection in Engine Mechanical-5.7L.

  6. #6
    Joe (Moderator) joecar's Avatar
    Join Date
    Apr 2003
    Posts
    28,403

    Default

    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.

  7. #7
    Senior Member
    Join Date
    Jan 2006
    Posts
    182

    Default

    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
    Last edited by ssvolvo; January 2nd, 2009 at 02:16 PM. Reason: Stupid country boy aftyer 3 beers.

  8. #8
    Junior Member
    Join Date
    Jun 2006
    Posts
    41

    Default

    Quote Originally Posted by ssvolvo View Post
    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.

    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.........
    Last edited by 10secvette; January 5th, 2009 at 05:47 AM.

  9. #9
    Senior Member
    Join Date
    Jan 2006
    Posts
    182

    Default

    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
    Last edited by ssvolvo; January 3rd, 2009 at 12:47 AM.

  10. #10
    Lifetime Member
    Join Date
    Apr 2007
    Posts
    272

    Default

    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.

Page 1 of 9 123 ... LastLast

Similar Threads

  1. New Guy with TCC Issue
    By OldGreg in forum 4speed RWD/FWD Transmission Tuning (incl T42)
    Replies: 4
    Last Post: November 30th, 2009, 03:21 PM
  2. LC-1 Issue
    By jermstyle in forum General (Petrol, Gas, Ethanol)
    Replies: 5
    Last Post: January 6th, 2009, 09:36 AM
  3. BBL and E38 COS Issue
    By swingtan in forum FlashScan V2 BB Logging
    Replies: 2
    Last Post: October 29th, 2008, 10:00 AM
  4. New Issue
    By jamesbond2509 in forum General (Petrol, Gas, Ethanol)
    Replies: 1
    Last Post: October 16th, 2006, 09:07 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •