1997 GMC Safari Rough running

1997 GMC SAFARI
240,000 MILES • 6 CYL • 2WD • AUTOMATIC
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JOHNSON VIKING
  • MEMBER
  • 1 POST
My safari seems to missfire.
This occures while cruising only....that is while doing about 65 MPH on the highway. It seems to accelerate fine and is ok when I let off the gas.

It seems to get worse in colder weather.

The problem is getting slowly worse.

Thanks
Dec 11, 2008 at 12:58 AM
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RASMATAZ
  • ✓Experienced Mechanic
  • 75,988 POSTS
Do you have a check engine light and when was the last tune-up ?

Misfires 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.
Dec 11, 2008 at 1:20 AM
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