misfire with no codes, need help please!

[mrialsm4]

ok guys, like the title says, I have a random misfire seemingly all in the 10"hg to about 5psi range.

it happens at very low load, but the misfire is sparse. at about 50% throttle it misfires pretty good, and at WOT it's hard to tell if there is any misfire at all. The misfire was non existent when I first took the car off out of the shop last week and it has progressively gotten worse over the course of a full tank of gas.

so far I've done the following;
changed plugs, plug wires, front O2's, and got some ohmic readings on my coilpacks and they were all consistent. I've checked the valve springs and rockers, and ran a compression check on the motor, all cylinders were spot on.

A month ago the car was running pretty good, with the exception of needing some idle tuning and a good autoVE. at this time I finally burned up my 3rd built 4l65, and figured it was time for a change for the better. I installed a TH400 with the supporting mods to support around 1000RWHP (RMVB, T-brake, 3800 stall). I also changed out all of my piping from my procharger to the FMIC to my throttle body.

the mods to the car are as follows-
lq9- 403ci 9.3:1
Ported fast 92 with stock DBW TB
95lb injectors @ 45PSI with versafueler driver box
Mast fuel rails with magnafuel pump and boost referenced regulator (not connected)
EPP FMIC
F1A procharger @ 16psi
Trickflow 225 heads
Kooks 1 7/8" headers/ no X pipe with 3" borla race mufflers (way too loud)
Harland sharp rockers
cam is- 224 int./230 exh., 0.581 int./0.588 exh.
TH400 with RMVB, T-brake, 3800 stall


What do you guys think that the next best course of action to take would be? I'm pretty much stumped since I'm not seeing any codes thrown, very strange......

Thanks for the help in advance, guys.

[mrialsm4]

9196

Here is a current log. It's short, but the miss is there during the cruising.
it was also my first AutoVE attempt after the new setup was completed.

[mrialsm4]

any ideas guys?

[joecar]

Your HO2Sx1 voltages show you are excessively rich at cruise...

(AFR_B shows 14.7 being commanded, but the HO2Sx1 voltages look like they would at WOT with an AFR richer than 12.8)

this might be the reason for your misfire;

also your MAP looks wrong (excessively low), which will cause the cylinder airmass to be mis-calculated;

it also looks to me like your injector tables don't match your injectors

(at part throttle cruise just past the middle of your log, the INJDC almost max's out... [with those huge injectors])

how much HP/TQ are you supposed to be making...?

[joecar]

Do you have a wideband...?

[mrialsm4]

No, they are not scaled properly. They are 2.5 times less than the 95lb rating, i had to a lot of doctoring to get it to even run. I have all of the airflow tables divided by 2.5, and am running a 2.5 bar map. In the log, the car is running olsd. It was my first autove with the new setup. I did put it back into cl fueling with trims and all enabled, and did achieve a lean cruise (14.7). The miss never goes away. Wideband is there. I logged it in the file. It's a plx.

[mrialsm4]

for some reason, no matter the AFR, I still get the miss. any ideas on what I should be logging to find the culprit? Let me know, and i'll post the log.
By the way, the reason I have everything scaled back is so that the large injectors will work properly with the "limited" parameters in the E40 ECM.
another funny thing is, when I was running a pretty much stock setup with SVO 42's the injector duty cycle was hitting outrageous numbers as well. my AFR was always pretty much inline with what was commanded after the initial AutoVE tune I did. I know that the 42's were enough for that setup, and I know that the 95's are enough for this.
as for horsepower, your guess is as good as mine. I modeled my engine build after this car-
http://www.exoticperformanceplus.com/projectCar.php?car=29
http://www.gmhightechperformance.com/features/0808gmhtp_supercharged_2005_cadillac_ctsv/index.html

[joecar]

Did you scale the MAP correctly...?

[joecar]

How severe/noticeable is the misfire (I'm try to get an idea of its magnitude)...?

Is it using up any coolant...?

[joecar]

You checked valve springs and rockers; what lifters, pushrods, rockers, springs are you using...?

You changed ignition components; did you visually check for spark using a spark tester like KD2756 (observe spark while snapping throttle)...?

You did compression test and all cylinders were sufficient and close.

I missed wideband AFR in your log, I'll look at it later tonite.

[mrialsm4]

I didn't scale the map, I thought that this would throw me back into the same predicament as I was having before, with the injector scaling. I was under the impression that this scaling was only used for the 2 bar os. Thing is, I really have made minimal changes (intercooler piping and running my air filter outside the engine compartment) and it was running ok before. The only major change was the th400 swap, which I can't relate to the misfire, right?
the misfire is VERY apparent. there's no mistaking it's there in the 50% throttle range and it's definitely there in the 25% load range, just like a slight bump every few seconds/ minutes. Have you ever had any experience with an old worn out 2 stroke outboard? I can compare this to the way that one of those runs when the carbs are gummed up.
I did check rockers, springs, and push rods. I still have the .025" preload on each lifter. The compression check was satisfactory in my opinion; 180ish, on all cylinders as I recall. The lifters are stock GM CTSV lifters. I can't recall the part number but they were recommended in several FI builds on various sites. The pushrods are hardened comp cams stuff.
I checked each coil by using the old screwdriver in the plug wire boot trick. All of them jumped gap to ground evenly. I did check each injector at idle to see if it was missing without me hearing it, I used the controls in the scan tool to cut each one sequentially and checked for tone change, i could distinctly tell when i cut an injector on each of the cylinders. so there is no miss at idle, and It's so hard for me to say if it is missing at WOT, because all hell is breaking loose, and I get tunnel vision, lol....... I don't think it is missing at WOT, I checked a couple of videos I had of it from earlier this year (in car) and it sounds the same to me, video to video.
The logfile is going to show the car running very rich, don't be too surprised when you look at it. it's the very first AutoVE. Nothing was changed in the tune except for raising the VE table 10% or so from the old tune

[joecar]

Wow, pretty wild...

I looked more closely at your wideband AFR, it is alot over rich... you're probably getting rich misfire...

Remove the plugs and see if they're all wet... what gap are you running...?

Do you get the rich exhaust smell...?

It's probably not missing at WOT.

You're using the LC-1 calc pid for your PLX, is this correct...? Is the voltage->AFR function AFR = V*3 + 7.35...?

[joecar]

Do you have FlashScan V1 or V2...?

If V2, then you should really be using serial comms to obtain AFR.

[mrialsm4]

I'm using V2. I am using an AEM wideband. the Calc PID for it is the PLX. I accidentally logged the wrong one; my brother's running the LC1 on his Firebird. I swapped the calc pid after i opened the log file when I got back home and it shows the proper AFR. I think it defaults to whatever I logged it with? I don't have any provisions for serial comms with the AEM, but I can swap my AEM in my car for a PLX, I have one in my 75 Bronco. it does have a serial port on the converter box I think. What would this do for me as far as accuracy? Plug gap is between .035" and .038" brand new plugs were used in this log and I did pull them out after the log and they were not wet. They just had a hint of blackening (soot) because of the rich condition.
I believe the calc pid for the PLX is - AFR = (V*2)+10?

[joecar]

V2 supports serial comms AFR from AEM UEGO.

I'm not sure how you connect it to V2, but there are only two possibilities:
- straight serial cable,
- null modem serial cable;

there's a thread on here somewhere for AEM.

Serial comms means V2 obtains the AFR from the wideband in digital form and so avoids AFR-to-analog translation/detranslation and analog voltage offset errors associated with that.

[mrialsm4]

I bought my V2 3 years ago, I don't remember this cable being included. Is it an additional item that I need to buy or was it probably included, and I just don't remember seeing it?
By the way here is the AEM hookup sheet for serial connect.

9212

[joecar]

Your V2 came with the 3 cables shown in your pic.

You need this cable (see the 4th one down): http://taquickness.com/taqcables.htm

You will need to update your V7 and V8 software from here (scroll down): Download Software (http://www.efilive.com/index.php?option=com_content&view=article&id=48&Itemid=124)

You will also need to update your V2 firmware and bootblock, please read attached doc carefully before proceeding.

What version firmware and bootblock does your V2 currently have...? This will determine what you have to do from the doc.

[mrialsm4]

see my software versions below.
I remember reading that document and going through those steps when I upgraded a while back. my versions should be sufficient, eh?
I'll see about getting that serial connection up and running. I feel much more comfortable with the idea of having a better handle on what my car is running the A/F department.

Can you suggest anything else that I would need to log, that I havent been, that might help in finding the misfire in the event that it's not an A/F ratio issue?
Like I said before, when it's put into closed loop the fuel trims do bring it back to a 14.7ish cruise, and the miss is still there. I just want to try and get it narrowed down a bit before I take it back out on the road. That's quite a bit of money under the hood sputtering and missing, Lol!

I'll post up as soon as I get the serial connection hooked up and get a log file uploaded; hopefully we'll make some sense of all this.

One more thing, I really appreciate your taking time to help me on this problem, it means a lot! I haven't gotten any help at ls1tech or the gto boards.

9214

[joecar]

You are correct, your software/firmware versions are sufficient, you're at the latest.

All you need is the cable mentioned in post #17.

[joecar]

You can also log the misfire pids, these attempt to identify the cylinder that is misfiring... you may want to do a CASE relearn first.

[joecar]

Misfires are difficult to diagnose... can you cause the misfire with your car stationary...?

[joecar]

When you get your serial comms cable, check the wideband AFR.

In the meantime, what do the spark plugs look like (pics)...?