I just finished swapping a JDM H22 in my prelude. from what I can see and feel in driving it is all good. The times on it are great, but there is an idle problem. The idle takes a long time to come down to around 800-900rpm I believe this is its normal idle. once it gets down there the whole car shakes. And at least 4-5 times a day while driving the idle will start ghoing up and down on its own when I am stopped. Any help would be greatly appreciated

 

Yeah I have been trying to get it to even out in idle. I will have to look at it. But I still dont know why it revs up and down when sitting still

 

check your pcv valve it could be clogged and also you said you did a swap make sure your ecu is for a MT. i got stuck with a AT ecu and it did something like that it runs good sometimes but every once and a while the idle is rough. just a couple of things to check out.

 

Mine also does this on occasions, it was fine for a long time but after I went to the track and ran a couple of times it started doing it again. The idle keeps jumping from 800 to about ~2000, what I did was disconnect the grey plug that connects to the IACV(idle air control valve) on the intake manifold, once I did that it idle'd fine but my check engine light came on so I plugged it back and then turned the car off and then on again and it was gone. Wierd problem I guess.