If you have been hit with the dreaded sticky high idle, (or are just doing maintenance), you may be wondering if you can get away with just cleaning the throttle body while it's attached to the block. I opened up the butterfly and gave everything I could reach a good wiping with a solvent-soaked rag.

It made the sticky high idle problem worse...

So I took off the throttle body. It's a little fiddly to get out, but not too hard. From the air side, it looks like I did a reasonably good job, although I missed some on the lower right edge of the butterfly.


Then there's the engine-block side....


Oof. I gave it thorough cleaning, being careful to keep the solvent out of the TPS. While I had it on the bench, I also did motorcarman's return spring modification.

So yes, remove the throttle body from the block to clean it. It's well worth the effort.

 

While the TB is off might as well clean the EGR valve seat as someone observed his idle " recovering "

This would have the same effect as the IAC valve too far open at it's idle position

But different gasses being O2 consumed somewhat in the EGR gas circuit

 

Good point. I wish I had seen your reply before I reassembled everything... While the TB was off I didn't remove the EGR valve but I did try to get the passage from the valve into the TB as clean as I could. That seems to have been good enough for my TB - between the cleaning and the spring tweak, my high idle problem seems to be fixed. (For now. Knock wood.). If it comes back, I know what to try next.

 

Oh to have easy access to the throttle body and not have it blocked in by a supercharger and intercooler!

 

Yeah, I cleaned the heck out of mine. Took it out of the car once, cleaned it, put it back in, still high idle. Took it out, again, cleaned it 5 times or so, cleaned EGR and set the throttle butterfly gap, and its better. I found cleaning the outside just as helpful as cleaning the inside. Even with the inside spotless I couldn't get the throttle plate gap as low as needed. It would stick if I set it to the "proper" gap. Cleaning between the exterior springs got it unstuck. Still needs calibrating but I got completely distracted.

 

Some have found from me reading the gasket missing on the IAC valve mating to the TB

There is a precaution on the IAC mount bolts snapping off

This would change the gap in the IAC poppet seat dimension as it schedules' down down to the idle position

Since it is a stepper motor it may come to rest at a higher opening then normal since the normal position may be too flow restrictive

Just spit balling without knowing for sure but Vee had an IAC valve reset / calibration procedure

And then we get to the ECU orientation with the special equipment if the TPS is out of matching the ECU's given null ( not 0 ) at idle