Having hi idle problem

[richy rich]

So I noticed a few months back the car[87 GN] would sometimes have hi idle,sometimes turning the car off and on again seemed to reset it.If the car was started cold and driven and not shut off it seemed fine.but on restart it may have had hi idle.So my Gn guru friend says ahh its a bad chip-so i threw in my TT race chip,problem gone[short drive],so I installed my old Red Armstrong street chip[again short drive]Thinking it was a bad Tt chip,I slept good.next morning[today]hi idle from the get go!And now worse than before!I tried all my other chips-still hi idle.About 1000 rpm warmed up in gear!vacum gauge reads 15[in gear]19 idle.Dont think its a vacum leak cause why would it go away before when i restarted it?I reset the tps to .44[was at 50].IAC seems hi?[60ish]
Could this be something with my IAC?Id like to "reset" if I knew how,or do I just change it?Any Jobber store unit ok?Am i barking up the wrong tree here?I got the old OTC 4000 plugged in to answer any questions where my numbers are at.
Just had car running and warmed up IAC at 40ish in park-toss it into gear and it shoots up to 73?02 at 43.
K so engine off key on-tps at 42 and IAC at 140.
I went and bought a new AC Delco IAC,installed it-car runs the exact same!!
same numbers
Thanks!Rich

 

[bad V6]

Mine idles the same way with the TPS set to .42. Try setting the TPS to .38 and resetting the IAC.

 

[richy rich]

OK,But How Do I reset the IAC?

 

[bad V6]

http://www.gnttype.org/techarea/faq/IACresetscan.html
http://www.gnttype.org/techarea/maintenance/TPS.html

 

[richy rich]

So I replaced the IAC w a new AC Delco unit.
I noticed the IAC #'s were zero.
So I reset the IAC as per the IAC Reset procedure bullentin.
When I started the car with the IAC unplugged[as per the bulletin]It ran at 3000RPM!
Not sure if thats normal so i left it there for about 30 sec.
shut off car and replugged it back in.
I got the IAC numbers at around 23.And the TPS at .40
Still idles hi??Sits at around a grand drop it in gear same!
I tried turning the AC on and it shot up at least a few hundred rpm.
Am I missing something here??

 

[bad V6]

Try backing the TPS down to .38, and see how it idles. Mine idles at 850-900, with the TPS set to .38 and the IAC set to 36.

 

[JayC]

TPS voltage is irrelevant as long as its below .48.

You might want to make sure its not floating when the engine is running. Ive seen a lot of cars do that if the grounds were questionable.

 

[blackdeathtrap]

bad grounds would be my guess
iv got hunch correct me if im wrong but could a leaky tb shaft gasquet cause this

 

[richy rich]

But if it was a mechanical problem such as throttle body gaskets.or warn throttle shafts,
why would it reset itself after shut down?
bad ground-interesting-I could check that.
Bad TPS?Wouldnt be a O2 thing would it?

 

[richy rich]

So problem solved-so thought I would write in to recap things.
Im guessing the IAC was on its way out-so I believe I was on the right track by replacing it.
The IAC needs to be reset even when replaced by a new one-didnt know that at first.
So I followed the IAC REST PROCEDURE bulliten.
I set the IAC numbers then the TPS numbers-all numbers looked great!
The last problem was that my OTC was NOT set on ROAD MODE!!!So it automatically kicks the idle up!
I ended up resetting everything[including the computer]-unplugging the OTC and taking it for a drive!
So after all that it was a bad IAC and me not knowing how to reset it-then that stupid OTC being in diagnostic mode!!UGGG!!
Hope someone can learn from this thread-I know I sure did!!