Before I begin, I have done a search on this and various boards and checked everything people have suggested to others. My issue is slightly different but very similar to others that I've read about. I keep going back to it being a vacuum leak but can't seem to find where.

The issue is: Usually the car will start and run great first start of the day. If you shut it off and run into a store and then come back out, it will fire up but within 10 seconds start to sputter. At this point I can shut the car off, start it back up and it'll run great. The reason that I'm concerned is it is getting worse. I'm now having to have to re-start it 2 or 3 times when warm, and also I have issues when its extra cold outside 15*F See Video Below


I've replaced the plugs/wires, MAF sensor, Bypassed Fuel Pump resistor and same thing occurred, cleaned the throttle body out (yes the IAC is cleaned and functional). The plugs looked pretty good considering they were 130k mile plugs, not overly clean or carboned up. I had my mechanic look at it this month when I had it in for a new exhaust and state inspection. After 3 days they were scratching their heads. No codes hidden or shown. According to him sensor readouts were there and seemed proper.

Any help would be greatly appreciated.

ICM'* when they go bad, its usually when they are warm that they fail. But work normal when cold.

If I am seeing things right, it'* looking like the misfire is there when you first try and rev it up too, and not just idle.

Given that it goes away on a restart, that makes me suspect it is something electrical. I have just gone rounds with a '98 Regal that seems to have a weird ICM, that causes the car to stall and do funky things. Then out of nowhere, it will run fine. Idle was also one of the oddities that it was encountering.

Assuming your mechanic is competent, it may be worth looking in to. The car will seem like it'* running rich (smelly exhaust) if it is getting a poor ignition. Vacuum leak won't.

thank you. I'll probably be giving that a shot this weekend if I can get to a junkyard. Thought maybe it could also be a clogged cat but removed the EGR and plugged the intake line and it still does it. So that points further to your idea.

Video of what I did:

It will run fine for about 10 to 20 seconds and then starts to chug and stall.

I hear the IAC opening up, that'* when it stalls. Pull the IAC out and see how clogged it is.

yeah, i did that :(

did that when I cleaned out the throttle body, and I verified that the iac was working.

got the gauge pressure is 48psi at idle, dips a couple times before stall and then goes up over 50psi while stalling. Also is it normal for the IAC to click like that with the key on and not running?

FP with key turned on and clicking IAC:

FP While running and stalling:

The fuel pressure increase is typical with the vacuum dropping. That may be a worth while check too, to see what manifold vacuum is doing.

If you do find yourself in the junkyard, maybe snag an IAC or two also. Mike might be on to something, especially after seeing the fuel pressure jump around like that.

That 2nd video with the fuel pressure jumping around at the end, next time it does that gently hold the throttle open and see if you can keep it running.

On another note, did you remove the TPS and reinstall it?

Not to resurrect an old thread but just wanted to say thanks for the help and posts from people. I hate to just throw parts at something but when you are at a loss and need the car...well..you know how that goes. I replaced the ICM and it ran stronger but still stalled. Around the same time that I did this the fuel pump seemed to take a dive as fuel pressure really started to drop off and the car wouldn't stay running at all. I replaced the pump and that fixed that problem but still had the stalling issue. Found a small vac leak but fixing made no difference. Running with MAF unplugged is not an option, the car will start and idle but crack the throttle at all and it stalls. Unplugged the TPS and still stalls.....thennnnnnnnnnn I unplugged the upstream O2 sensor....runs like an absolute dream. I'll replace that soon as I get a chance and see if that fixes it, until then just going to run with it unplugged. Again I wanted to say thank you for those who chimed in with ideas and suggestions.