Start-up Hesitation Until Computer Reads From O2 Sensors

[ninjaneer]

1999 Silverado 1500 4wd 5.3

 

When it's warm outiside or when the truck is warm, immediately after starting and pulling away it will rev up but won't shift. I used a scan tool to check out what the engine is doing, and after the computer comes out of warm-up mode (ie, the computer starts using the oxygen sensor readings to adjust trim), the throttle will respond like it should.

 

Any ideas how to fix this? Is it a ground issue? Does the computer need to be re-flashed or updated?

 

No codes are being thrown.

[ninjaneer]

Anybody? I know I'm not the only one to experience this, based on an unanswered post here and there.

[95Sierra2500]

I've got something similar in my old '95. It just kinda hangs a bit sometimes before it even tries to shift. I've found that letting off and getting back on it takes care of the problem. No clue what the problem is, but it seems to work just fine.

[bossier62guy]

1999 Silverado 1500 4wd 5.3

 

When it's warm outiside or when the truck is warm, immediately after starting and pulling away it will rev up but won't shift. I used a scan tool to check out what the engine is doing, and after the computer comes out of warm-up mode (ie, the computer starts using the oxygen sensor readings to adjust trim), the throttle will respond like it should.

 

Any ideas how to fix this? Is it a ground issue? Does the computer need to be re-flashed or updated?

 

No codes are being thrown.

 

I've read your post about 3 times now and I'm still not sure what you're talking about LOL. You state it won't "shift" and then talk about throttle response being restored to normal after the engine enters the closed loop mode. I do know that if it was a ground issue you'd have the problem whether or not the engine was in the closed or open loop mode. Is it a transmission problem or a throttle response issue?