I have a 2008 Chevrolet Tahoe Hybrid. 6.0 4x4. It has AFM (Active fuel Management) and before you get to thinking this is a simple misfire. think again... The Misfire is on cylinder #3 a Non AFM cylinder. The motor was rebuilt 40k miles ago and had the lifters changed and all that. The plugs are new, coils are new, wires are new, I've moved around fuel injectors. and I've done a compression test and cylinder 3 wasn't too far off maybe 10-15psi lower. The part that really throws me for a loop is (besides not finding the misfire) the fact that sometimes the truck runs great. no misfire what so ever. It will run and drive just fine... 15-20 miles later the check engine will flash (still run fine) then the CEL will stop flashing and turn completely off again and continue to drive great. then whenever it feels like it the truck starts misfiring again. sometimes the misfire is hardly noticeable.. sometimes is very violent and causes other cylinders to throw a misfire (low value like less than 20) Also it only seems to misfire when its at idle. (well that's when its at the worst anyways)
so like i said. everyone I've talked to doesn't even know where to begin. I have a cheaper obd2 scanner that I can get graphical or live data with...
Well since the pressure it can be 15 psi lower there's obviously a problem in that cylinder do a wet and dry compression test of that cylinder first. No of course it could be a bad fuel injector you could swap them to see if that's the problem or it could be the fuel injector wiring harness I've seen them go bad on those lots of things can do it
I actually pulled ohm tested all the injectors and they were good. just to be sure I pulled the fuel rail and moved them around a bit. I will do a wet compression test and let u know what i find out.
dry and wet compression test.