2000 Pontiac Grand Am Misfires on 3 cylinders

Tiny
TREFLIP98
  • MEMBER
  • 2000 PONTIAC GRAND AM
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 172,000 MILES
I have a 2000 Pontiac Grand Am Se with 172,000 miles. It has a misfire on 3 cylinders. At idle it runs rough and low. As I accelerate more it seems to be much smoother. Also I get horrible gas mileage when it's supposed to get 20-32 mpg. I've replaced the plugs, wires, coils, and the ignition module. It also shows no signs of a leaking or blown head gasket. Could it be the fuel injectors or computer?
Monday, July 6th, 2009 AT 2:37 AM

1 Reply

Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
Have PCM scanned at most autoparts stores for free.

Report any codes. Other sensors that are out of range will cause a rich mixture and misfires, coolant sensor for example.

You also could have a clogged CAT.
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Monday, July 6th, 2009 AT 8:27 AM

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