2002 Pontiac Grand Am - multiple misfire?

I have a 2002 Pontiac Grand Am that recently started idling really rough and I lost about 4-5 MPG in the last two months. The last two days (really cold days) I would warm it up for about 20 - 30 minutes before driving, going about 10-15 miles and it would stall on me as I came to a stop. I took it in to a mechanic today and they changed out the plugs and were convinced it was the ignition module. It turns out it wasn't the module, but they are clueless as to what it could be, they just know the computer diagnostic came up as "multiple misfires" but don't know why. Does anyone here have any clue? More info can be given if needed. Thanks in advance.

2008-01-03T12:50:19Z

Ironhand - The only code they mentioned was a multiple misfire, and when I asked about the fuel filter (thinking that might help also) he said it was showing nothing wrong with the fuel system. Thanks for taking the time to answer :)

2008-01-03T12:59:15Z

Mrabtrus - it may have started hesitating more recently with the acceleration, but nothing major. Whats more noticeable at times is the way it might "hesitate" while going a steady speed.

Ironhand2008-01-03T12:46:10Z

Favorite Answer

1) Fuel Quantity (fuel filter or fuel pump)
2) Fuel Quality
3) EGR Valve defective
4) Coil pack
5) Plug/coil connectors or insulators
6) ???

It would be good to know what other codes were stored (cleared?) along with the P0300.

?2015-08-12T23:01:21Z

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RE:
2002 Pontiac Grand Am - multiple misfire?
I have a 2002 Pontiac Grand Am that recently started idling really rough and I lost about 4-5 MPG in the last two months. The last two days (really cold days) I would warm it up for about 20 - 30 minutes before driving, going about 10-15 miles and it would stall on me as I came to a stop. I took...

MrAbstruse2008-01-03T12:51:32Z

I had a Pontiac Grand Prix that did the same thing. I think it's your Catalytic Converter. Is it slow to accelerate?

deadhead76762008-01-03T12:44:40Z

This sounds like your timeing belt is off. It usually causing stalling when in idle and can cause misfiring and very high or low idle.

Anonymous2016-03-22T20:16:18Z

I would suspect the spark plug wires. My 1997 GTP did good until I replace the spark plugs then the wires started to short to ground. Any good quality wire will work But the correct leingth AC delco wires is what I went with.