91 Civic DX with MPFI swap and a home-made turbo set-up @ ~5-6 psi. This problem began as sort of an on and off occurrence.

Car starts, runs normal, until it has been driven for a few minutes; at which point, the engine begins to race. It is most noticeable when I put the car in to neutral. The RMPs may be at a normal level while in gear, but as soon as neutral is engaged, at a stop light or for a gear shift, the RMPs jump to 2000-3000.

Eventually I begin getting CELs that always include Oxygen Sensor. As far as I can tell, nothing is out of place. This problem happens without going into boost. When the engine is idling high, I can bring it down by lifting the gas pedal up with my foot. This led me to believe that it was a mechanical problem, however, nothing I have tried has helped.

Idle has been adjusted, throttle return spring seems OK, throttle cable soaked in oil, added second spring to gas pedal return spring. Nothing has helped. I'm running out of Ideas. I have searched and have not found anything addressing these same symptoms. Any ideas would be very much appreciated.

 

I removed and cleaned the Idle Control Valve with carb cleaner. No help. Anyone have any ideas?

 

Anything?

 

check for vacuum leaks and bad map sensor

 

I have checked everywhere for a vacuum leak. Can't find anything. Whats the best way to test the status of the MAP sensor? What would make it cause this type of problem?

 

adjust ur idle screw on ur throttle body??

 

Yes, adjusted idle w/screw. I can get the car to idle OK when I first start it, no CEL's. But as I drive it, the RPM's want to go real high, as if I have my foot on the gas pedal, even when I don't. This is made even more obvious when the car goes from being in gear to neutral. The RPM's will jump from say 1500 to 3000. Sometimes, i can get the RMS's to come down by quicky depressing and releasing the gas pedal, as if the throttle plate is being "bounced" closed....

 

FITV? (fast idle thermo valve)

Bolts to the bottom of your throttle body.

Might be worth checking the voltages of your TPS too.

 

if pulling the pedal fixes the problem then your throttle plate is getting stuck open due to carbon build up most likely. get a brass bristle brush and some carb cleaner and clean the opening of the throttle.

 

I tried cleaning the Throttle Body with cleaner, but didnt think to use the brush; Ill give it a shot. Any suggestions as to the best way to verify the functioning of the FITV?