Car doesn't idle when it's cold
 

Hey everyone. I have a 2000 Trans Am, manual. Little background and what's going on.. Got into the 20s here and car wouldn't start. Bought a new battery and it was fine for maybe 3-4 days and then it started but then it idled really bad for 10 seconds and eventually died and wouldn't start again. Got a little warmer out, maybe 40-50ish and it started and ran just fine. Got off of work and it was cold again outside and the car started but wanted to die again, so I needed to keep giving it gas constantly to keep that from happening. Car warmed up and there was no change. Still wanted to die. Hit every stop light on the way home, all 11 of them, and wanted to die at every one. I don't know if it being cold outside has anything to do with it but that seems to be a common factor. What should I check first? I haven't heard of something like this before so I don't know where to begin to troubleshoot.

You need to move to South Florida.

Really....can you find someone locally to scan your PCM with an OBDII scanner while the engine is running? Sounds like the same issue another member is having with air-flow. It sounds like your IAC is closing up on you. Maybe an issue with your IAT sensor giving the PCM bad information causing the PCM to close the IAC too much when you are off the throttle and its stalling.

If giving it pedal to keep the engine alive...means that you're giving it that little bit of air it needs to stay running....means the IAC valve is closing for some reason when you are not giving it pedal, and the IAC is choking the engine and stalling it.

Could just need a new IAC valve....but with these freaky cars, it could be many things causing it via bad info going to the PCM.

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going to run to Autozone or O'Reilly's when I get off of work tonight if all goes well. Get some codes.

Sounds like running airflow table is off. Has it ever been tuned?

running fine for now, which is weird. i didn't mess with anything on it.

it just has LTs, duals, and a SLP lid, haven't got it tuned for those yet

Wonder if the alternator is on it's way out. or you have a draw on it slowly killing the battery. Sounds like a batt bad symptom

went to autozone to have the alternator tested after i put the new battery in. alternator tested fine on their little gadget. but who knows how reliable that is though

Have you checked fuel pressure? Smoke test for vacuum leaks?

fuel pressure no, and i need to test for vacuum leaks. what is the psi supposed to be at?

Close to 58. You'll want to do a key in engine off to see what it builds to then key off and see if it drops off fast. If it never builds then fuel pump issue. If it builds then drops, likely a leaky injector, check valve, or dash pot.

Then, start car and make sure it holds at least 54 while idling. Rev a few times to make sure it holds. Shouldn't drop even under full load.