i know there have been a number of topics on this but ive never seen anyone with the same symptoms as mine so please read on.

recently swapped a 93 d16z6 into my 91 crx running a p28

car had a rough idle after the swap so i did plugs wires cap rotor and that didnt help so i seafoamed it really good and now the idle is intermittley surging and 90% of the time will idle about 1100 rpms...i know what your thinking clean the iacv and ive done that twice and it helped a little but it still is no where near right.

the other day it was surging (completely warm) and i pulled the electrical connector off the iacv and the surging stopped and then started as soon as i plugged it back in.....then i drove it home and pulled into the garage and pulled off the intake and put my finger over the lower hole (for the fitv) and i got a little suction but it did not change the idle so i put my finger over the iacv hole and got good suction and the rpms dropped but the car wouldnt not die even after i covered both holes

ive screwed the white screw in all the way on the fitv and i only have this problem after it warms up so it has to have something to do with the iacv but what?

the car idled at a normal 750 after the swap it was just a little rough i didnt really get any surging until i seafoamed it

 

Any excess air that enters the motor can cause this idle surge. Vacuum leaks, IACV, FITV, EGR not seating when closed, bad PCV, throttle cable too tight, and idle screw out too far can all cause a high idle. When the idle exceeds ~1200 RPM with the engine warm and the throttle plate is closed, the ECU cuts off the fuel injectors. The idle falls below the threshhold, the injectors cut back on and the whole cycle starts over again. I had a starting boost valve(accord) that was leaking through the diapham that caused mine. Something like that can only be found with a vacuum pump/guage. Anything that has a vacuum line running to it can cause this problem if it won't hold vacuum, not just the vacuum lines and gaskets. This includes EGR diaphram, Boost valve diaphram, cruise control, MAP, Intake bypass valves, Purge solinoids and others depending on model.

 

after i seafoamed it i put a aftermarket intake on it...do you think the extra air comming on through the k&n filter could be the cause?...if so is ther anyway to compensate for it?

 

Keep this in mind...

If for any reason the cars idle increases to about 1100-1200 or more rpm with no throttle change (tps idle voltage constant) the ecu cycles the injectors on and off just like a rev limit. That is what the surging is. Find out why its getting extra air.

The iacv is very sensative and has to be very clean with not a spec of debris. Sometimes seafoam and other cleaners can dislodge carbon and cause issues.


EDIT: wow our posts are strangely similar....

 

yeah i was sure to clean the iacv very good after i seafoamed it....and on second thought i dont think it could be the new intake on it because it only does it intermittenly

 

That intake wont cause it. Air leaks on the other side of the throttle plate do.