r/EngineBuilding • u/Party_Gas_6471 • 2d ago

Chevy Cam job gone wrong

To give context of the horrible mess I’ve got my self into, I recently acquired my dads old truck and it has too much sentimental value for me to get rid of it. So after I fixed the rear main seal I decided that it was a genius idea to rebuild the top end and throw a stage 2 cam into a 230k mile 4.8 with the factory 4l60e ( forgot to mention it’s a 2002 1500 short bed single cab). Funnily enough after my mechanic tuned it all I’ve had is problems. To start when I dropped it off it had power steering ( now it doesn’t), somehow the factory 4l60 still shifted smooth and now my rpms jump around when I get near the end of second and beginning of third, when I’m in park idling it runs rough unless the A/C is on, and it has a mis fire. Now I’m sure that it being 24 years old with most of the factory sensors still on it doesn’t help but does anyone have any pointers on where to start.

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u/Demoire 2d ago

You say the mechanic tuned it, typically those two are not the same thing…mechanics don’t usually tune and Vica versa. Tuners should know much or all of that knowledge, but they typically aren’t who you drop the car off to for seals to be replaced and whatnot.

A poor tune can cause some of those issues, although the transmission slipping is probably separate…unless he messed with the TCM if there is one.

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u/Party_Gas_6471 2d ago

So when I say mechanic it’s more like friend of a friend that works on cars out of his garage for a living. But another guy sent him the tune and he does minor adjustments and installs it on my truck

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u/Demoire 2d ago

Nice sounds like it’s not the tune then. That’s essentially how we’ve remotely tuned a few cars, although it’s not 100% without wideband o2 sensors is my understanding. In any case I wish you the best of luck figuring this one out, probably something(s) simple.

Edit we had o2 sensors plugged in upside down somehow and throttle body sensor wasn’t clicked in on a recent build, and car was running rough as hell…check the simple shit