Question about 2003 GMC Envoy

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Engine knocks cold ok hot

2002 envoy I6 4.2 engine knocks when cold

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If its at the top end its pistion slap
if its at the bottem end(of your engine) its a crank shaft bearing.

with out going into extream detail,

a ting sound at the top is a pistion slap.... replace all your pistions posibly over hual the engine.

a dubble knock that gose with rpm but sounds 2 knocks very every fireing of the pistion is a crank bearing..... replace your crank shaft bearings.... all of them b/c metal gose threw an engine extreamly fast and will destroy other beraings. this knock on start up will turn into a knock all the time, then a very louad knock that will end your engines life.

unfortunetly the answer is engine rebuild and fast.

Posted on May 30, 2009

  • Ryan
    Ryan May 30, 2009

    this is an early sing for pistion slap an worn out bearing on your crank shaft.

    if it gose "ting ting" at the top of the engine realy fast at ilde its pistion slap.... you need a new pistion

    if it gose knock ... knock at the bottem and seams to be at the top and bottem but still close to the bottem end and changes with engine RPM and seam to almost X2 as fast as the RPM..... this a bearing. you need act fast, bearing are metal when they break or waer out they can send more metal to other breaings down the road. soon you will have alot of kock and all the time. you need a new crank shaft bearing.... problem is what one ? so you best replace all of them and do the engine over haul.

    to avoid this in the future let your car warm up befor the drive it, ESPECHIALY in the winter



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secondly take a small screw driver aor a tiny hammer and tap the valve while the engine is running if it smoothes out replace the valve the valve is carbon filled and needs to be changed .

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