Fast Idle Drops When Stopped
 

Good afternoon all,

I have a 1990 4-door Accord with a 5-speed manual I picked up from an auction a few weeks ago. Overall it runs great and I am thrilled with it (our "driver's ed" car!). There is one problem with the car that has us stumped. Any time the car is rolling over, say, 2 mph, the idle speed picks up from about 850 and goes to 1500 or so. As soon as the car stops again, the idle drops back to where it is. It does not appear to be linked to anything other than speed. When stopped on a hill, without touching the throttle, regular brakes or anything but the parking brake, as I release the parking brake and start rolling, even slightly, the engine revs up. As soon as we stop via the parking brake, not touching anything else, the idle drops down about 2-3 seconds after stopping. Any ideas?!?

Thanks in advance!

Detlef

First clean throttle plate (both sides), throttle bore around plate, and idle air control valve (IACV). See DIY section for help.

After cleaning, suggest adjusting the idle speed as per the manual (see Online Manuals download for a 90-93 manual) ; fully warm engine, disconnect IACV, and adjust idle air bypass bleed screw (top dead center of throttle body entrance) to get 600 +/- 50 rpm on tach. Reconnect IACV and reset ECU by pulling BackUp fuse for 15 secs.

If you have problems, someone may have adjusted the throttle plate idle stop which is not supposed to be touched at any time. You will have to manually reset by trial and error until idle adjust procedure works.

good luck

Actually, that might be a "feature".

A large amount of HC emmissions occur during the lift-throttle part of shifting, & most cars have some means to reduce this. Older cars had a dashpot on the throttle to prevent it from closing fully, suddenly.

I don't know 1990 very well, but it probably has an air valve somewhere that's controlled based on the VSS. Any signal from the VSS indicating the car is in motion, it probably steps up the idle.