Having issues with my 99 camaro z28 m6, car will crank but barely is holding an idle. Idle bounces around between 300-450rpm and has a miss. This issue was intermittent but has become a constant now. With the low idle the car has misfires when holding the rpm’s at 2k and has shown itself to change sides from odds to evens with the scanner.

I’ve tried cleaning the TB and maf, a new IAC, a new tps, and a new battery with no luck in resolving this issue. The reason I swapped in the new battery was because this happened about a week after putting all new speakers/subs/amps into the car. Verified fuel pressure is 55+ at idle and with rpm. All ground check out good.

Getting codes:
p0353
p0300
p1637

Any advice on something to try as a resolution would be greatly appreciated.

 

ignition coils and plugs should be the problem

 

I would agree with you but the miss fires aren’t consistent to one bank or one side. I can have it missing on evens, turn the car off, close and reopen the scanner and when running have misfires in a different bank or side.

 

unhook the MAF and see if it acts any different.

what's the BARO sensor PID show?

What's the MAP sensor show, key on, engine off

 

would be easy to test the coils and look at the plugs

if they are older, it's a good idea

MAF would probably show MAF codes or lean codes. you are showing misfire

 

With the maf unhooked it acts no different at idle, tomorrow I can upload a data log of the low idle and readings as well as how the misfires are showing.

 

Plug wires are fairly new, plugs I would like to believe are as new as wires (previous owner). I have a set of tr6’s I can swap in to rule the plugs out

 

My suggestion is to assume that your problem is closely related to (result of) your wiring for the new speakers/subs/amps.
Make sure you have +12V going to the PCM, to one side of the injectors, and to the coils. (Sorry don't know offhand which coil wire that is).
Make sure your grounds are good, e.g. a volt meter shows 0.0V difference between the engine block and the Battery Negative.

 

Unfortunately all of those ideas checked out good, no difference in voltage when comparing battery posts to ECU, Injectors, grounds, or coil harnesses.

 

Went to pull a data log but figured I’d check the error codes first got a p0302 so I reseated coil connector, pulled/cleaned/gapped spark plug, reinstalled plug wire. That codes now gone as well as the p0300, still having the p1637. But not it is idling like it should, just hoping this will be permanently resolved and not come back again in a day or two.

When I was disconnecting the ECU to meter wires it seemed a lot easier coming off than before. I’m thinking maybe I somehow didn’t get it fully seated when I put it all back together after running the audio wiring. Perhaps it vibrated loose and caused intermittent connection to? I’m just grasping hoping that’s the solution and that I’m not back on here later today.