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TBI Issues...

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Poohbair

1/2 ton status
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TBI 350 in a friends truck. Throttle feels very sticky when the engine is running. Replaced throttle cable, and it is still crappy. The throttle feels fine when the engine is off... but as soon as you start the truck the throttle sticks and the TBI wont shut all the way.

Any ideas why this would be any different w/ the engine running than with it off?
 
How is the IAC valve looking? It might be sticking instead of the throttle cable...

If not the IAC, is the cruise control on the fritz and pulling the throttle part way open for some reason?
 
there is no cruise. IAC could be on the fritz..... that would make sense why it only does it with it running.... i never tried it with only the key in the on position... if that would matter.
 
IAC doesn't move the throttle plates themselves...if no cruise, I can't think of why the throttle plate would be sticking open only when it was running. I'd try disconnecting the throttle cable and working the TBI with the engine running see if it is replicated with the cable out of the picture.

Having a hand on it (with no leverage) might show another problem.
 
The butterfly may be hitting the wall of the tbi. I had to file slightly on my holley's. I got mine out of wack when I was beating on the shaft of the tbi.
 
dyeager535 said:
IAC doesn't move the throttle plates themselves...if no cruise, I can't think of why the throttle plate would be sticking open only when it was running. I'd try disconnecting the throttle cable and working the TBI with the engine running see if it is replicated with the cable out of the picture.

Having a hand on it (with no leverage) might show another problem.
Click to expand...

Wasn't thinking so much about the IAC moving plates, so much as it messing with the idle and making him link the plates are sticking open, even if they arn't.

I can't think of any reason at all why a throttle body's throttle would stick while running, but not while it isn't running...
 
Yeah, I gathered by "throttle feels sticky", that the cable was swapped out, and "throttle feels fine when the engine is off" that it was pretty well narrowed down to something mechanical not related to electrical stuff.

I see where you are coming from though. :)
 
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