4.3 5spd will not drop idle at stops.

[joep88cheyenne]

When I come to stops my engine doesn't idle down. I can kick the throttle and it drops but not on its own. Kinda like the fast idle cam on the carbs, but i have TBI. 88 4.3 5spd. Not nodded.

 

[evilunclegrimace]

Is the CEL on? Do you have any stored codes? Does the idle stay high if the truck is not moving and you bring the RPM's up and release the throttle pedal? If so check for a binding throttle cable and make sure that nothing is interfering with the linkage at the TBI unit. Also check to see if the carpet and/or the floor mats are interfering with the pedal.

 

[DerekTheGreat]

In addition to that, get yourself a scanner. I had a high idle problem with my '89 350 TBI 5 speed truck and threw parts at it before diagnosing. New TBI gasket, intake gaskets, cleaned the IAC blah blah. Problem still persisted. Seriously pissed me off big time for a long time. Then, I called down, hooked my MT2500 and just watched the data. Sure enough, my TPS was going wonky and it's voltage was switching from ~0.65V to as much as 0.85V on it's own with no actual throttle input. When it did that, I could see the computer adjust the IAC counts. Boom, there's your problem lady! Replaced the TPS and low idle function restored.

 

[RichLo]

since it goes down when you pop the throttle it sounds like a mechanical problem as said already in this post. Broken spring, rusty or sticky throttle shaft, floor mat, binding cable, etc.

 

[joep88cheyenne]

No cell, mats are vinyl and flat, pedal clears them. I will check springs and throttle movement at TBI unit.

Thanks looking for a starting point and got some to check on the cheap for now.