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1999 Silverado 5.3 lost power

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Today I was driving and my service engine soon light came on then I went to give it gas and there was most of its power gone I pulled over waited about 20 minutes, truck started right up, idled perfect, oil pressure 40, so I drove the truck home barely any power foot to the floor the whole way home. But 3 days ago I did cut the muffler off to take measurements for the new one I planned to put on today, I don't know if that could've affected anything. any information would be awesome thanks

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Have the same thing happening with mine. It's just fine 85% of the time but 15% of the time it feels like I have absolutely no power to even get up to speed. Gave codes P0135 and P0300. Yours may be similar if you get them read.


I changed plugs and wires and it didn't fix. My fuel pressure is good also. Took mine to shop and he suggested coils may be bad but he wasn't confident enough in the diagnosis to actually change them for what it'd cost.


Staying tuned, hopefully you get your answer and I can leech off of it! ;)


P.S. I'm still on stock exhaust so exhaust may not be the issue.. who knows.

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Okay so I took the truck out and the only gear I have is drive, I do have reverse but in drive it feels like just one really long gear, if I put it in 1, 2 or 3 it changes nothing it just continues in drive, I've checked every fuse, I undid the battery, the tranny was rebuilt new 30,000 miles ago. So I don't think I blew the tranny

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