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Hey guys, i recently did a Head swap on my 2001, using PRC 225cc heads. The swap went relatively smooth but my car is now misfiring. there is no check engine light for it (service abs and tcs did come on after about an hour when i got home). car mostly misfires under load and it’s pretty violent. the car will shake at 50 with the converter locked and it’s pretty sketchy. idle even sounds weird(it’s a cammed car but has a completely different cadence then it did before). any help would be appreciated
Other than changing plugs and wires you don’t have the advanced diagnostic equipment to fix this…you will only waste time and money…seek out an auto diagnostic shop !!…Jake will fix it !!
I deleted your new post since it is a duplicate…which cylinder or cylinders are misfiring and are they “companion cylinders” or next to each other in the firing order ???…you can swap parts you want but is the wiring for the coils ok ??…did you check injectors (injector balance test) and wiring ??…if its mechanical and if you find a shop that can identify which cylinder or cylinder’s are misfiring and can perform incylinder testing the engine may have to be torn down…with incylinder testing I can tell what is mechanically wrong in a few minutes WITHOUT engine tear down…this can be finding a wiped cam lobe or valve issues…compression testing is not 100% accurate as it only tells you the cylinders ability to seal…I gave you the name of someone who can do this type of testing and it’s not a dealership or a grease monkey mechanic as they will only guess and change more parts…below is a old waveform on my 2001 and I annotated the valve opening and closings based on the waveform…also resistance checking is NOT how it’s not and I don’t know what you are checking here…a ground wire for instance can have all but a few copper stands remaining but ohm out fine…unfortunately we can’t diagnose this for you !!
Lots of undisclosed history. You have reached out to the forum with many specific issues, received specific advice, and never reported back on the resolution. I suggest you provided feedback on how the previous issues were resolved.....because the issues could be related or compounded. Also provide detail of how you went about swapping the heads.
I deleted your new post since it is a duplicate…which cylinder or cylinders are misfiring and are they “companion cylinders” or next to each other in the firing order ???…you can swap parts you want but is the wiring for the coils ok ??…did you check injectors (injector balance test) and wiring ??…if its mechanical and if you find a shop that can identify which cylinder or cylinder’s are misfiring and can perform incylinder testing the engine may have to be torn down…with incylinder testing I can tell what is mechanically wrong in a few minutes WITHOUT engine tear down…this can be finding a wiped cam lobe or valve issues…compression testing is not 100% accurate as it only tells you the cylinders ability to seal…I gave you the name of someone who can do this type of testing and it’s not a dealership or a grease monkey mechanic as they will only guess and change more parts…below is a old waveform on my 2001 and I annotated the valve opening and closings based on the waveform…also resistance checking is NOT how it’s not and I don’t know what you are checking here…a ground wire for instance can have all but a few copper stands remaining but ohm out fine…unfortunately we can’t diagnose this for you !!
I can get access to advanced diagnostic, i swapped to new 48lbs injectors and the issue persisted even after the swap (and being tuned for the injectors) i believe cylinder 1 and 3 are misfiring. we turned the misfire counter on and 1 had 73 counts, 3 had mid 40s, the other cylinders were in the teens. something else is that i have new ls7 lifters and there is a tick, but this tick was persistent before new lifters. the total build has maybe 250 miles on it since the heads/lifters(has been cammed for well over 20k miles before the head swap). i’m just kinda unsure, i don’t like taking my car to others. is there any advice you could give for doing my own diagnosis? plugs didn’t fix the problem, coils didn’t fix the problem, plug wires ohmed fine. something else strange is that the car broke up pretty bad after 6200 rpm+ on the dyno, power dropped off and got wavey (looked like valve float even though i have brand new .660 lift springs).
Getting access to the equipment is one thing and knowing how to use it and interpret what you’re looking at is quite another…after almost 20 years learning and doing this advanced diagnostics I’m still attending classes either online or in person so you’re NOT going to figure this out on your own in a week !!…watch the 3 part C6 Corvette video on how a misfire is diagnosed…the tech in the video is not real sharp but this is all the testing I normally do with the equipment…the only advise I can give you is let a professional diagnostian get your car running right…in the video he is trying to “current ramp” the coils and injectors with a “fuse buddy” but he pulled the wrong fuse…LOL !!…he pulled the backup lamp fuse.
Help!! Misfire ??
