Very high idle TPS problem

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xj0hnx

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So my buddy that bought the hatch rebuilt the motor, new block, old head, and now it's running, but, it's got a really high idle. We've hit all the usual suspects, coolants topped off, and bled, MAP/TPS aren't backwards, vacuum leaks all fixed, IACV removed, thoroughly cleaned and replaced. When you unplug the TPS sensor nothing happens to the idle, we're guessing that's the culprit. Is there a way to recalibrate it, or adjust the shaft one way or the other to lower the idle? or does it need to be replaced? And how does that work with it riveted to the TB? Replace whole TB? if so, that's teh ghey
 
Check the idler screw... it may simply need to be turned in a bit on the TB to close the butterflies up a bit.
 
If u unplug the tps nothing happens? Sounds like a wiring issue, check the tps for power and work back till you find out where it isn't going to.

I suspect the wiring harness is the culprit
 
The TPS isnt riveted on, they are shear screws. If you need to remove them grind a slot so you can take them out with a flat head.
 
If you loosen up the tps mounting screws it can be adjusted, jus have your + lead in the center wire with the key on and motor not running. U should have .5 at closed throttle and about 5 v at WOT
 
In my opinion....the riveted TPS wouldn't need adjustment. If the TPS is off.....I would suspect its not out of calibration but simply bad/broken. I could be wrong but I would do other stuff first.....like re-set the idle.

Get car to running temp (fan comes on at least once). Turn motor off. Unplug the IACV electrical connection. Re-start car. It should idle around 450-500rpms with IACV Unplugged. If it is higher....then I think this may be the issue. With car running and IACV unplugged, now you can adjust the idle screw to the desired rpm (450-500rpm). Then turn motor off, unplugg back-up fuse or disconnect ground for roughly 30 seconds, re-install and plug IACV back in. Start car up and see where she idles. If this doesn't help then I would try to dremel out a flat head groove in the TPS rivets and unscrew it so you can try to calibrate it. Just be ready b/c it may need replacement
 
In my opinion....the riveted TPS wouldn't need adjustment. If the TPS is off.....I would suspect its not out of calibration but simply bad/broken. I could be wrong but I would do other stuff first.....like re-set the idle.

Get car to running temp (fan comes on at least once). Turn motor off. Unplug the IACV electrical connection. Re-start car. It should idle around 450-500rpms with IACV Unplugged. If it is higher....then I think this may be the issue. With car running and IACV unplugged, now you can adjust the idle screw to the desired rpm (450-500rpm). Then turn motor off, unplugg back-up fuse or disconnect ground for roughly 30 seconds, re-install and plug IACV back in. Start car up and see where she idles. If this doesn't help then I would try to dremel out a flat head groove in the TPS rivets and unscrew it so you can try to calibrate it. Just be ready b/c it may need replacement

Ran through this procedure and when we unplugged the IACV the idle dropped to a pulsing idle between 1200 and 1500. Adjusting the idle screw had absolutely no effect on the idle whatsoever, none. Turning it out we kind of thought we heard an increase, but if it was, it was only about 0.3 rpm. We're pretty sure the TPS is the problem, but we have to get a new gasket before we take off the TB to remove it, and try testing it specifically.
 
So, the problem has been found (sorry Ryan I have to), but not without exhausting every other possible lead, and honestly we would have never found it if he hadn't decided to tear down the engine for another rebuild ...the bottom row of bolts on the IM were never tightened. So remember kids, measure ten times cut once, always take your time, and be thorough, tighten everything twice, and have someone else go over it once you're done.
 
Ah......:shrug2:.....I have done stupider things.
Like shut my hood with the oil cap on the valve cover and dented my hood
 
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