Rep Power: 0

My Honda civic 2001 LX will idle high ( 1500 rpm) then will drop down to 750 after coming to a complete stop when driving (fully warmed up). When sitting still if I hit the throttle it will idle at 1500, for about 5 seconds, then drop back down to 750. I recently re-did the A/C system. had to pull the ecu to remove the evaporator core and replace the expansion valve. I don't remember if it was happening before or after the A/c fix.
I pulled at IAC and cleaned it. Cleaned the throttle body and checked for vacuum leaks ( none found). After I cleaned the throttle body and IAC (were not very dirty) I tried the ecu re-set a couple times. I just returned from a road trip (over 600 miles ) and still have the same issue.
- it doesn't stall or is not effected by a load (a/c ).
It feels like something is telling the IAC to change the idle rather than a vacuum leak. very sharp change in rpms.
no check engine light.
valves are in spec, iridium plugs, good air filter, good coolant.
car runs good, just idles funny.


I have a new IAC coming but not sure it will fix the problem.


any ideas??


Thanks.

 
Rep Power: 518

Idle relearn done?

 
Rep Power: 0

Did it twice.

 
Rep Power: 0

Compression is good too. Cranked 6 times at WOT. 155 160 165 165.

 
Rep Power: 0

Ever figure it out?

 
Rep Power: 0

I got a new iac. It was bad. Cleaned and installed the old one. I shorted the time I ran it after re setting the ecu. Only ran for about 1 min if that. Then shut it down for a few seconds, fired it up and runs good. Idels nice and smooth at 750.

 
Rep Power: 0

Hmmm. My car is acting similar to yours. I believe he cleaned the IAC though.