Honda Car Forum

I have a 1990 honda accord ex 4 cylinder automatic and it has a problem with the idle. when started cold fast idle is good for a short time then it wants to go up and down constantly until I hit the throttle hard then it will drop down and stay there.....until i put it in gear and push on the throttle again . then it will run at fast idle again (power brake)until i put it in neutral and the motor will rev up and then the idle will drop again to normal. it also wants to pulsate driving at slower speeds like driving around town. very frustrating to have to put in neutral at every stop light or sometimes just to slow down to a slower speed.

Help please.....TIA

I believe thaT is the (IAC) idle air control valve,you can try and clean it out.

OPERATION
The Idle Air Control (IAC) valve controls the engine idle speed and dashpot functions. The valve is located on the side of the throttle body. This valve allows the necessary amount of air, as determined by the Powertrain Control Module (PCM) and controlled by a duty cycle signal, to bypass the throttle plate in order to maintain the proper idle speed.
TESTING
Turn the ignition switch to the OFF position. Disengage the wiring harness connector from the IAC valve . Using an ohmmeter, measure the resistance between the terminals of the valve. NOTE: Due to the diode in the solenoid, place the ohmmeter positive lead on the VPWR terminal and the negative lead on the ISC terminal. If the resistance is not 7–13 ohms, replace the IAC valve.

Thanks, I will have to check that out. i eventually found a thread about this and where to clean(for a surging or hunting idle) but they didnt really address having to put it in neutral to get it back to normal idle. when you go to accelerate from idle i can feel it grab the throttle and accelerate on it's own....just a small amount....seems like the applying the brake affects it also.


thanks again

Try to clean the IAC valve with PB Blaster or gumout to remove the carbon. IAC valves are very expensive and I never see the electrical part go bad. You have to revove it anyway.

Thanks I will try to clean it better...I had it off once and cleaned it half a$$ed...almost seemed like it made it worse but I think I will try test the resistance as given above and if it checks out i will take it off completely and clean it better.

Thanks again for the response