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Random mutiple missfire

thousand dollars later

Random mutiple missfire

Postby 4low [OP] » Aug 22 2015, 4:31pm

hi guys,

I bought this truck after my wife picked it out, gona be making payments for 4 more years, and i really like it! She has good taste! After taking it through a mud hole in 4 low motor pinned for about 5 seconds the check engine light flashed and came on. Im a diesel mechainc so i was a little concerend, figured it was a loose wire or something minor, check engine light was code p300, hooked up a nice scanner and found 4 cyls missfiring, replaced plugs wires, and coils. still missfiring at idle and some times power loss. ive drove with this problem for 6 months checking all wiring, cleaning all sensors. finally i took it to the dealer and they found cyl 2 and 7 had valve leaks. both had 120 psi. they want 1700 to remove the heads and inspect. so i figured i can do that in about a day my self, but when i pull the heads, why dont i just get new valves, guides, and springs, and a more agressive cam to bump up the hp to 400 from the stock 300. I just cant figure out what cam and springs to purchase. I will be talking with a machaine shop about what im after, has any body found a kit like they have for 350s? And with 140000 thousand miles, should i just pull the engine and complety rebuild it? Id like this engine to last about 10 years as a daily driver.
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4low
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Location: Eugene
Year: 2001
Make/Model: GMC Sierra
Extra Info: 5.3
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