2001 Other GMC Models Random missfire

2001 GMC
295,000 MILES • V8 • 4WD • AUTOMATIC
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JULES77
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  • 1 POST
cylinder #4 and #6 , missfire .
i changed spark plugs , wires , cleaned the injectures , change the gaskits on the intake manifolt, swich the coils between bank 1 and bank 2 , changed the CMP sensore , change the fuel and air filter , and i changed the lifters , and i still have missfire on those two cylinder, , any idea, thx
Sep 3, 2010 at 7:45 AM
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RASMATAZ
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  • 75,992 POSTS
Engine running rough or misfiring can be cause by the following:

1.Defective spark plug
2.Inadequate spark/coil,defective spark plug wire.
3.Lack of compression
4.False air leakage.
5.Faulty fuel injectors.
6.Insufficient fuel pressure.
7.Contaminated fuel.
8.EGR valve that is leaking.
9.Oxygen sensors.
10.Throttle position sensor.
11.Idle air control valve.
Sep 3, 2010 at 9:51 AM