rehaf

For those with OBDII cars, a crazy acting Idle Air Control Valve (IACV) can make driving miserable. I've had a recurring check engine light with a P0505 and some crazy driveability problems for a few weeks. I finally had some time this week to look through the Honda service info and take care of the issue. I just wanted to go over what I done to repair my car in hopes it may help others. I have a D16Y8 with a stick in case it matters.

A problem or a misadjusted idle control system will cause symptoms like:
*A rapid dip in idle speed followed by idle up
*Hunting idle
*A near stall condition with the driver's foot basically just resting on the throttle, this can cause the engine to jerk badly at times when driving.
*A check engine light

First of all check for and repair any vacuum leaks and clear any DTC's. Clean the throttle body and IACV with the appropriate cleaner. Warm your engine to operating temperature and turn it off. Unplug the electrical connector from the IACV and restart the engine (in neutral or "park" of course) and note the rpm. You need some sort of accurate way of reading rpm, don't go by the factory tach. I used a scan tool that also reads engine data. Make sure the a/c is off and the power steering isn't in a bind, you don't want any load on the engine. Adjust the air bleed screw on the throttle body until you get 700 rpm +/- 50. Shut the engine off, reconnect the IACV, disconnect the battery for a few minutes the reconnect it and start the car and drive for a few minutes. Normally this should take care of the problem and the ECU will relearn the correct idle speed.

My problem went a little deeper. I bought my car used and the previous owner apparently tweaked on everything including the throttle stop. So I had to restore everything. If you find yourself in the same situation, here's what I did. I started by unplugging the IACV and turning the air bleed screw all the way in. The rpm was still 150 or so too high. I loosened the throttle stop slowly until the engine stalled and tightened the jam nut. If you have a scan tool that reads data or a multimeter check your throttle position sensor signal. I had to tweak mine a little after I moved the throttle stop to get the correct closed throttle voltage, ideally it should be 0.49 volts. I screwed out the air bleed a couple of turns so the engine would start. Then I was able to use the air bleed screw to properly set the rpm and finish the repair.

Maybe this can help somebody having the same problems. If you have other techniques post them up.