I have a 2006 ss sc. Throws a random misfire code. It has an extremely rough idle, AFR is all over the place, and I’m getting god awful fuel mileage. However it’s perfect under WOT. It has new coils and spark plugs. I saw a post that said if you cleaned the throttle body that it would help, tried it, no change.

Currently running a zzp cai, #60 injectors, 2.8 pulley, long tube header and full exhaust.

I’m starting to think crankshaft or camshaft position sensor, vacuum leak or tuning issue. I’m not the greatest mechanic so I could be way off. Any help would be appreciated!!

 

Were any plugs Fowled when you changed them? Is it tuned properly for all the mods you have or have you added anything without re tuning?

 

they definitely didn’t look great, but I think they were okay. I had a base map put on it years ago, I ended up selling the car and I bought it back recently. No extra mods have been added since then. It started misfiring before I sold it and I just figured I wouldn’t have to deal with it anymore but here I am 🤠.

 

If a specific plug keeps fouling I would try the coil packs and check the wiring going to each pack on the valve cover they have a tendacy of getting brittle and cracking

 

I know the coils are all good, I’ll check the wiring though. I think I might also just start throwing a little money at it with the cheap problems first, (MAF, MAP, etc.) just in case.

 

Couldn’t hurt. It could even Be a bad 02 sensor or an injector not working properly. Do you run a wideband?

 

Yessir I do. However everything is on hold as of now, battery just took a ****. 😎

 

Grabbed a new battery, hooked up my new code reader. P0304 cylinder 4 misfire. I’m reading a lot of people saying that it’s a bad valve possibly which would suck. But I have a hard time believing that because it runs perfectly fine WOT and I’m under the impression that it wouldn’t if there were indeed a bad valve.

 

Pull the plug on 4 and check it out, if it looks fouled you potentially have power issue to the coil. Or fueling issue on they cylinder. Could be as simple as cracked wiring for coil or bad injector seal what’s your afr look like when your getting misfires under normal driving conditions?

 

Tossed the plugs but they didn’t look great, can’t remember exactly. AFR’s jump around from 13.2 all the way to 16.3 under normal load. WOT it’s at 10-11. I swapped the number 3 and 4 coils around, code went from cylinder 4 misfire to random misfire.

edit: it just jumped back to p0304 on its own. So in other words it’s not the coil pack itself. It’s also started having random 10 second intervals of no misfires and normal AFR’s at idle. Weird.

one more edit: found an exposed ground wire on the wiring for the connector on the number 4 coil pack, guess that’ll do it. Been shorting out this whole time I suppose. I’ll take care of it and give an update.

 

I would try and get a log to see what your trims are. You are running super rich on WOT and lean at other times.