Every once in a while when I start my car the idle cycles from high to low - probably for about 1 second on each. High is maybe 2000 rpm and low is about 1000 rpm. When I engage the transmission it goes away. Any ideas?

1990 Accord LX

 

Replace idle air control valve with oem part.

 

Don't replace. Remove and clean. Screw the "wax ball" back down tight and you should be good.

 

And use the search feature to find a thread on how to do this. Or just check the stickies.

 

I would just replace the IACV considering age and miles on car. Besides, you already have it off the car.