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Misfires!! Urghh

R

rickisrad

New member
I am chasing a random misfire that is not setting codes. I have swapped out the ICM, coils, plugs and wires all separately to try to eliminate the issue. I have tried multiple case learns. I have a newer Maf that is clean and reading correctly. What am I looking at next? ECM?
 


How bad is it? Is your converter new or the original? (looking at probability that it's getting clogged and not working at its best)
 
Thanks. I have a hollow converter. The misfires are strong enough to really bog down on hard acceleration.

I don’t think it’s the injectors. They are AC Delco OE that has less than 30k on them. I also run Shell v power 93 octane with archoil fuel additive.
 
Are you seeing more misfires on one cylinder? Maybe it's another bad icm? Have you tested the spark with a test light? Do you see anything weird in the scans when it acts up? I'd take a look if you posted it. Do you have to crank for awhile when the car sits?
 
It will also stall out because of this issue. Seems usually at turns?????

Bandook- it misfires on random cylinder and usually all of them. I have tested spark but can’t when it is acting up because it mostly does while driving. My HPTuners won’t log misfires so I can’t see those on a scan. I will scan it and post the results here. The car starts right up at all times.

Scottydogs- I have not seen any significant knock during all this. I am going to get a scan on it soon.
 


How in the hell do I upload the file here?

Scottydogs, I did have some KR in this scan.

HPtuners sucks. I can not log misfires and it freezes often. Their support is worthless.
 
Did this just start happening? Or have you made tune changes? I don't know the 07 pcm, but first thing I noticed is how high your timing is under part throttle. Also, do you live around a lot of hills? I mean, I kinda know cleveland. Didn't think it was hilly. I'm gonna have to download a stock tune to get familiar. If you want to post your tune that would be cool. Obviously, if it was fine on the same tune, then that's not it. Maybe this year is just that much different than what i'm used to.

I'd probably start by looking for vacuum leaks. Your trims are pretty high. if it was spark related, you would have negative trims, right? You are getting knock on decel too, which i think i've had when i had a big vac leak. Just spitballin', so take it for what it's worth.

Also are you using a wideband? Self tuned/dyno/canned?
 
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