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1999 GMC Sierra skipping

Tiny
QUAGMIRE
  • MEMBER
  • 1999 GMC SIERRA
1999 GMC Sierra Z71, 5.3L 105,000 miles
Idles fine. Runs smooth until it reaches 55 mph. I can maintain a smooth 55mph, but when I press the throttle slowly to speed up it misses badly (enough to jerk your head). When I get about 57-60 mph it stops. Only happens at about 55-56 mph. I can be parked and throttle up to the same RPM as the highway speed and there is no problem. I'm not sure if I can explain it any better, its like RPM is not part of the problem.
All I have checked is to be sure the plug boots are on tight. Any help is appreciated.
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Sunday, July 23rd, 2006 AT 10:10 PM

3 Replies

Tiny
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  • 10 POSTS
I changed the spark plugs and wires. It seems to have solved the problem.
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Tuesday, August 8th, 2006 AT 10:24 PM
Tiny
PYROMATICX
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I have the identical truck and just changed my plugs tonight, and mines still doing it. I usually drive in 3 because ive never liked how my trans shifted in D but on the highway I usually throw it in D. Once I hit about 55-60, it jerks, not in rythm, almost like im towing another car and there hitting the brakes on and off.

Maybe 4th has gone bad and I never notice bc im always in 3rd?
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Thursday, September 14th, 2006 AT 6:28 AM
Tiny
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Change the plug wires and see if it helps you.
I was told by the local GMC Service Manager (a good friend of mine also) to change them at 100k. He said they start to break down in that range.
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Friday, September 15th, 2006 AT 8:48 PM

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