Thread: P0300 help - engine misfiring and stalling upon startup

I've got an '02 GTP with just over 120k miles. I had 2 codes, P0300 and P0130. P0130 was for the upstream oxygen sensor, I just replaced that yesterday so that should be good. Second is for the engine misfiring. I know there are some other threads on this but I wanted to see if anyone had some ideas with my specific symptoms. The car starts up no problem, but a few seconds later it dies. It eventually stays running, seeming like once it gets warmed up it performs better. Still, it isn't running smoothly and rpms fluctuate when idling.

Going in order of obd-codes.com, here's what some potential problems are:
Spark plugs: I haven't actually tested the spark plugs but they were just replaced at 100k miles so that wasn't too long ago.
Spark plug wires: I didn't replace the wires when changing the spark plugs as the looked to be in good shape then but I tested the wires with an HEI tester today and they performed just fine.
Coil pack: I got a coil pack, tried swapping in the new one in each of the three positions with no luck.
Oxygen sensor: Just replaced the upstream one since that is what the code was pointing towards.
Faulty fuel injector: have not tested
Burned exhaust valve: have not tested
Faulty catalytic converter: have not tested
Stuck/blocked/leaking EGR valve/passages: have not tested
Faulty camshaft position sensors: have not tested
Defective computer: have not tested

Do any of these have a higher chance of causing the engine to stall immediately after startup? Or does anyone have some direction on what to test next?

Idle air control ... Mass air ... closed loop issues are tough to trouble shoot sometimes.

Sent from Ohio

Originally Posted by Fivefingerdeathpunch

What brand plugs?

If you have the ablilty to do so, swap ICM's with another 3800 car and see if it runs better.

The plugs are ACDelco 41-101. I don't know of any 3800 I could swap with to test..

Originally Posted by jimzssei

Idle air control ... Mass air ... closed loop issues are tough to trouble shoot sometimes.

Sent from Ohio

Ok, so I've got some new information that might direct this better. I picked up some mass air flow cleaner. Took out the sensor, sprayed it, let it dry, put it back in. Started up the car and it sounded pretty good actually and stayed running, the rpms were not fluctuating. So I let it go a few minutes and it sounded fine. Turned it off, let it sit a few minutes and tried again. Same thing. Stepped away for 20 min, came back and tried to start it, it would turn on then stall again just like before. Hmm. So I took off the MAF sensor, cleaned it again and put it back it. The car ran. So then I wanted to drive it around the block and see how it did. I made it about 100 feet and the engine stalled. It gave no indication it was struggling, just died. So I got it going again and now it is back in the garage. So close to having it fixed.

Could this mean I just need to replace the MAF sensor with a new one?

Originally Posted by DualDrillMe

New maf possibly. Do you have access to a data scanner? see if the maf is reporting data?Unplug the maf and drive it. see what happens. Dont romp on it just drive

I have an OBD2 scanner and the torque app on my phone. MAF sensor was giving a readout of 212.5 g/s sitting in the garage. Then I unplugged it and drove it. I kept low rpms and stayed under 20mph but it never stalled and seemed to run okay.

I ordered a new MAF sensor and it should be here tomorrow. So I'll replace that and see how things go. I just started it up now with the maf sensor unplugged. The rpm's were still fluctuating but it wasn't low enough to seem like it was going to die. Is this common with having the sensor unplugged? Should it still flutter like that? Or am I looking at an additional issue?