5.7L engine replacement 97 tahoe

[CG97Tahoe]

Do I need to reprogram the ECU after putting in a new motor? Replaced the 5.7 with a reman longblock.

 

[SunlitComet]

same engine specs? no changes except to say disconnect power to pcm for a minute or two after change but of course you would have already done that getting the engine out by battery disconnection right?

 

[CG97Tahoe]

Yes and yes, same engine specs. It's a direct replacement. I ask because everything runs smoothly break in went good but it is showing symptoms of a bad ECU. It isn't throwing any codes but jerks a hair on an up shift. Just fixed this problem in a van by replacing the fried ECU. Wanted to make sure it didn't need reprogrammed before I buy a new one.

 

[SunlitComet]

kill the battery power to the pcm again and give the engine a few miles to relearn stuff. see if it comes back.if so we can diagnose.

 

[CG97Tahoe]

So as far as killing the power am I able to just unhook the battery or do I need to unhook the pcm directly? If so ive done this a couple times and so far no change. The best way I can describe what it is doing is. When you come out of a corner and accelerate to lets say 45 as soon as it shifts up and the rpms drop a second later it will do a sudden but light jerk and sometimes even feel like a hard shift. No noticeable loss of power though and it only does it once it's warmed up. The transmission should be fine. No leaks or burnt fluid and didn't have any problems before I put the new engine in.

 

[CG97Tahoe]

And it doesn't do it constantly its on and off

 

[SunlitComet]

what gear is it doing it in?

 

[CG97Tahoe]

what gear is it doing it in?

3rd gear, on the upshift. After your in 3rd and cruising it will do it here n there.

 

[SunlitComet]

any counts in the cylinder misfire history?

 

[CG97Tahoe]

Nope, my scanner isn't picking up any codes, no data stored and all sensor status' are OK