Question about 1989 GMC Sierra

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My 89 gmc sierra runs rough dosn't idle good (lopes)back fires till you get up to speed, when you hammer it it acts as though it gets flooded. I installed new plugs, cap, rotor, and fuel filter.

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Check the magnet inside the distributor for cracks.. If its cracked it fools the module into thinking it has more cylinders than the engine actually has the piece the rotor sits on just under that you will see the 6 or 8 points ..the magnet is sandwiched under this plate check it carefully and if you see a crack you will have to replace the distributor shaft. or go get a used one but check it to before you install it .......lol good luck.hope this helps..

Posted on Nov 30, 2009

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Assuming the spark plugs were right, and the heat range was right, it sounds to me as if you might have a broken valve spring...that will also cause a misfire like that as well....you could try a comporession test or try removing your valve covers and inspecting the springs...if one is broken, then that will need to go to your mechanic as this could be costly..there are short cuts you can take, but i dont think a job like that is for a home mechanic simply because of the complexity of the task..but i didn't see that replaced any spark plug wires with that? always do that if you're going to do everything else around plugs...wires are the most ignored, tune up part, and certainly one of the most important...try new spark plug wires, no change, pull your valve covers, and inspect your valve springs...

Posted on Nov 19, 2009

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Could be a map sensor or an ignition module

Posted on Nov 19, 2009

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