Question about GMC Sierra

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2000 GMC Sierra V8 4.8L - I recently had my fuel pump & fuel filter replaced. I just changed my spark plugs and wires. Truck starts up fine, but it idles low now. When I'm driving it now hesitates some when I'm giving it gas, but if I floor it, it doesn't hesitate much. I checked all the wires to verify they were'nt loose. Any idea what to do?

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  • beshields Apr 04, 2011

    Air filter in good shape. Never checked PCV valve...not sure where it is and what to look for? Could the problem be I need to change the timing or are the plugs not properly firing? Just trying to rule out as much as possible. Thanks!

  • beshields Apr 05, 2011

    I put some stp fuel cleaner into my gas tank with half a tank full of gas. If it was bad gas, when should I see improvement?



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What shape is air filter & pcv valve in? That and run a good fuel system cleaner through it - there seems to be ALOT of questionable fuel going around these days. Am hearing it from all over.

Posted on Apr 04, 2011

  • beshields Apr 04, 2011

    Air filter in good shape. Never checked PCV valve...not sure where it is and what to look for? Could the problem be I need to change the timing or are the plugs not properly firing? Just trying to rule out as much as possible. Thanks!

  • Mical Caterina
    Mical Caterina Apr 04, 2011

    Pcv valve should be in valve cover w/hose coming from it. Plugs sound like they're good, you might try changing timing. Real trick for timing (for power & mileage) is to use a vac gauge, and advance timing until you get the highest reading, then back it off 3lbs of vac. It's an old GM trick, that when they age the dampener ring on crank pulley(Where timing marks are) actually moves and isn't as accurate as when new. If you do it with vac gauge make sure it's at normal operating temp.



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SOURCE: my engine hesitates when slow

i had the same problem and i replast the cap and roter and it is fine naw

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SOURCE: Tailpipe BLACK , exhaust reaks of gas !

garage mans company.
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SOURCE: I have a 2004 GMC Truck that misses or hesitates

If you are sure its not the plugs or wires, I woud go with the coils next, test each one, if they check out ok then perhaps the injectors.

Posted on Oct 08, 2009

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