Ecotec 2.4l COP misfire when warm

[Nicholas H]

Good evening everyone,
I have a somewhat strange issue that i am hoping someone has some insight into. I have worked out all of my other bugs thus far except this last ignition misfire problem that arises after running the car for a period of approx 15 mins. If i allow the car to sit and idle the miss appears sooner than if i allow the engine to idle for a moment then drive it. The misfire becomes more noticeable with more heat. The misfire only appears around 1400-2000 rpms and otherwise doesn't seem to miss a beat in the other rpm. I have tried a set of new coils, cleaning ground lugs, changing plugs, changing dwell, and changing timing and fuel around the problem area. I have restarted after getting gas (up to temp and heat soaked) to have it clear itself up when it was misfiring but this was only one time.
hardware:
This is a MS2 with 3.0 board
5v logic level spark output using TC4427 in wasted spark configuration (spark A cyls 1 & 4 and spark B cyls 2 & 3)
coils are 2005+ ecotec COP with pn#12578224 they have very similar plugs to LS2 coils (12v ign, 5v sig, ground, ground)
I have dwell set at a very nominal 2.2 ms and 2.5 ms cranking.
Inverted spark going high on wasted spark (not wasted COP which i am not sure exactly the difference there).
Starts and drives rather nicely when not misfiring. Normal mornings i can make it to work without a hickup. (10-15 min drive)
I have read some on the VAG coil issues and mine seams to share similar symptoms but i cannot imagine ecotec COP being much different than the very successfully used LS coils being they were made in the same time, have similar if not identical plugs and made by the same company.

Please, if you have any suggestion to help find the issue with these coils please let me know. I do not have access to an O-scope so unfortunately that makes me a little limited as to what i can see with dwell but i do have plenty of fluke multi meters.
I have uploaded the current tune but given the symptoms i do not see it as a tuning issue. But i have been wrong in the past.
Thank you in advance,
Nicholas

[slow_hemi6]

Try to get a datalog of the issue.

[Nicholas H]

Attached is a zip file of the last data log that had the missing prevalent. Ignore the idle hunt and the lean AFRs. I tuned out the idle hunt a couple days ago and the lean AFRs were due to a slightly dirty fuel filter. The time areas that i noted which the car was missing occurred at 408 sec, 540 sec, and 580 sec. There were of course other times within the data log but those were when TPS was constant and the data is most easily dissected.

Thank you

[slow_hemi6]

May be it needs a little more Accel enrich threshold (50 ish). A few bumps of AE kicking in where it is not really needed. Not much else I could see.

[Nicholas H]

Thank you for taking a look. I tried a little more accel enrich thresh hold this morning but it did not help unfortunately. Even tried bumping it up to over 100 just to eliminate a variable but still no luck. I appreciate your thoughts though.

-Nicholas

[slow_hemi6]

Last night I was specifically looking at your log where you told me but I reviewed it this morning and you have lost sync twice in that log (when cruising) at 937.9 and 1013.5 reason 51. Those will definitely feel like misses.
http://www.msextra.com/doc/pdf/html/Meg ... .4-87.html

[Nicholas H]

Ah i do see those. I haven't actually been looking at sync loss recently after having had to do everything i did with the vr wheel. This engine uses the 6+1 gm trigger wheel on the crank and so after having fixed the reverse polarity wiring the first time, then having to add a resistor on the signal wire after having sync loss at rpm above idle i have had a clean rpm signal since. Being at the end of the tune and during idle i'm pretty sure those sync losses were when i was burning a tune to the ECU but i do appreciate you looking at it. The miss i am experiencing causes a rhythmic bucking depending on the gear it is in and sounds like an overly rich engine on decel with the popping and burping (a persistent miss once per cycle or . Not an absolutely abrupt spark cut as it sounds some have experienced but possibly a late spark or something similar. I am considering my next step to be running it until it misses and swap out the coils for another set of cool coils to see if it stops missing while the coil packs are cool. This way i can at least narrow down where the issue might be. It just seems to have a coincidental correlation between missing and letting the engine compartment get up to temp. I decreased the dwell even more tonight to see if it would help down to 1.8 ms but to no avail.

Thanks agian for taking a look into this
-Nicholas H

[Nicholas H]

So just as an update, I discovered my problem was not the coil packs after having replaced the coil packs after reaching temperature and running the car again with no change. I then tried changing from 2 squirts to 4 squirts per cycle. This richened everywhere which actually made the miss nearly disappear. With having discovered this I went back to 2 squirts and added a good amount more fuel to the cells around my problem areas. After some tuning adding fuel the miss has went away. I guess I just didn't try adding enough fuel to the right spots before. It must have been a combination of engine temp and mat temp that leaned it out enough to not like it after hrat soaking. The afr was still close around 14-14.5 where it was having a problem and now with an afr of 13.0 I have no mis or any abnormal popping. Coil packs are running well with 2.3 ms dwell.

Thank you,
Nicholas

[Nicholas H]

So after 3 days of running well, the misfire returned. The misfire is extremely faint while warming up and slowly progresses as everything warms up. I thought for a while the injectors were at fault but they all ohm at 12 when cold and 13.4-13.6 ohm after it is warm and misfiring. I thought these values to be acceptable and I am now wondering if it is at all possible the ms2 processor is crippled? This board did experience a diode that was installed backwards on the injector circuit causing a path on the pcb to be cooked and later fixed. When the misfire went away I never hooked the laptop up after that to eliminate the possibility of a bad tune or bad burn. Without having touched the tune the misfire returned after 3 days. This points me to a physical part being the culprit. Let me know your thoughts even if they seem crazy.

Thanks,
Nicholas

[dontz125]

If switching from 2 squirts to 4 increases the amount of fuel injected, your dead time is too high. This will also affect things like warmup curves etc.

[Nicholas H]

That is some good info to know. I did learn a little more about dead time looking into this problem and it appears the advertised dead time for these mototron 80 lb/hr injectors is around 0.9 where i have the defult 1.0. I am still having the issue of the misfire and have started another thread on that where i have tried reducing timing, increasing dwell, adjusting fuel, but to no effect. I have limited the problem down to a heat soak issue with some component. When the car is cold the misfire is extremely faint and can hardly be heard. As the car warms to operating temp around 195 the misfire becomes more evident but still not terrible but after parking the car for around 3-4 hrs the misfire becomes extremely evident and audible. At this stage i can even feel the misfire lower in the rpm around 1300-1400 rpm up to 3000 where as when cold i can only pick up the spot around 1800-2200. My thoughts are towards injector issue or megasquirt issue. The high z injectors measure 12 ohms when cold and 13.4 when hot and the car has been acting up. All are within 0.2 ohms of each other when warm.

Thanks,
Nicholas H