LS4 Driving me CRAZY!!!!
 

So the car in question is a 2005 GXP had a random misfire when I bought it. I replaced plugs which looked like the originals, wires, cleaned the throttle body and maf, new air filter. Problem went away for half a drive around the block then came right back. I took all the injectors out and cleaned them (rigged a setup to run carb cleaner through them like fuel via a spare battery I had). put them back no change. I turned my attention to the coil packs, learned that the bank closest to the firewall was not firing at all. I switched the packs around same bank had no change. The next day I start the car it runs fine take it on a test drive and no sooner then the half block mark same crap!!!! Bring it back home pop the hood unplug the coil pack I suspect and the car stops. turns out its the front bank now!!! SO now I am thinking maybe a cam sensor issue, replaced it no change. Then I noticed that crap was coming out of the exhaust, turns out it was honeycomb from the converter. Car had a heavy fuel smell to it but didn't think it would kill the converter. I replace the converter with a ZZP unit, brand new o2 sensors and replace the exhaust piping from a car I found in the junk yard. Still same issue with the car only now it runs sometimes and sometimes wont even start. I swapped the CPU with a unlocked one and no change. Last thing I can think of is the crank sensor after that....... this car may be coming apart to try to get some of my money back out of it. Has a rebuilt trans in it to w/10k miles on it. Any and all help is appreciated. Thanks in advance.

Car is 14 years old, seems like you have replaced or tested the usual culprits. Maybe test voltage at the injector connections? All under hood wires become brittle in time and these cars have issues with heat soak. At some point you will need to stop replacing parts and bring it in for service if you can't get in front of it.Good luck, post back your findings.

I had a random misfire and I didnt replace what you did, but I tested everything you have replaced. I disabled DOD/AFM and presto vuah lah, no more misfire. Worth a shot atleast, and probably cheaper than everything else you've tried. It definitely cured my misfire issue. Hope this helps.



-Spain

Well the car is in parts now. Time to put a listing in the for sale section.

Are you going to sell it whole or part it out? Where is the car located?

Did you make sure you don't have a vacuum leak? or air coming in anywhere after the MAF? Does the misfire go away if you run the car with the MAF disconnected?
Oh car is in parts My bad