1999 Pontiac Grand Am Engine Misfiring

Tiny
MIKE51W
  • MEMBER
  • 1999 PONTIAC GRAND AM
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 13,600 MILES
About a two months ago, the motor was running very rough and engline light came on. I took it into the shop and they determined that the #1 Cylinder was misfiring. The said that there was oil in that cylinder and that I would need to change the engine because the seals were bad. Instead, we replaced all 4 spark plugs and cleaned out all the cylinders. That seemed to fix the issue at that time. It started to show small signs of a misfire for about a week now but no lights came on. Today, it had alot of hesitation on acceleration and by the time I got to the residence, it sounded like more than 1 cylinder was misfiring. It actually won't start unless I hold gas peddle to the floor, but then idles real rough and stalls. Any thoughts? I was also running fuel injector cleaner through it, and that seemed to help at the time.
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Wednesday, February 10th, 2010 AT 8:28 PM

1 Reply

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Engine misfiring can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.
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Thursday, February 11th, 2010 AT 7:20 AM

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