still haven't come to a decent conclusion with my 89 civic si..i put a stock 88 crx si motor in that was having the problem of every once and awhile the idle with go from 700 rpm all the way to 3-4k rpm for no apparent reason. it has also done this while cruising in 5th..the car feels like it's pulling itself with no throttle applied, then when throttle is applied it tries to choke itself out. no codes. any ideas? i replaced the o2 sensor, but no change.

 

try cleaning your idle air control valve. its the cylinder thing on the upper rear of the t/b held on by 2 10mm bolts. spray the screen w carb cleaner an reset ecu put it on and see if it works. i had to take the one off my crx motor and use it on my b16 but it fit and has idled fine since! ps it has 2 small coolant lines going into it.