08 Pontiac grand prix 3.8L V6 running rough out of the blue


Asked by Jun 26, 2015 at 11:49 AM about the 2008 Pontiac Grand Prix

Question type: Maintenance & Repair

I was driving my car this morning and it
was running perfectly fine. Stopped
somewhere. Then when I got back in my
car and tried to start it. It did not start right
away and is all of a sudden running rough.
Like it's missing. When I'm driving it seems
to be fine. But when I slow down and idle
it's running very rough. Car has a light
shake and sounds sputtery. Any answers?
Answers as fast as I could get them would
be nice as I need my car to get kids and get
to work.....

5 Answers


Sounds like MAP sensor or MAF sensor. if these don't work test the ECM

1 out of 1 people think this is helpful.

I just went and had it put on a free diagnostic. They said it had random cylinder misfire. They said it could be spark plugs, plug wires, or coil packs. So I get to check or change those.

1 out of 1 people think this is helpful.

How'd it go? My mechanics have been going back and forth on my car. I have one mechanic that has hooked my car up to everything to no avail or probable cause. But when I think it's gonna work; it doesn't. I have another mechanic that will replace my starter module and plugs that may or may not fix the car. I have the car start up most of the time but have to floor it to get it to start sometimes. It also sounds like it's misfiring when I go uphill.

April Carlson

2005 pontiac grand prix gtp supercharge was running perfectly fine. Got done working my car was running really rough where i would the car in neautral sitting still to prevent car from dying. Had my car in neautral at a stop light and i heard a short whinning noise and car shut down and I am unable to get my car started again.

April Carlson

How do I go about changing the plenum

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