I have a '90 Prelude Si with a JDM B20a in it and I can't for the life of me figure out the idle. It used to bounce between 1k and 3k which I thought was the IACV or a vacuum leak. Over the past week or so it's gotten worse to the point where it bounces up to my two step at 4k and even when I'm shifting, the RPMs shoot up for the brief moment I'm not in gear which makes me worry about the clutch burning.
It idles like that without the IACV installed at all so I assume that's not the issue although unplugging it makes it idle rough at about 1.5k and it runs rich. It's not the FITV either because I already messed with the big plastic screw.
There's only 1 vacuum leak that's small so there's no reason for it to go that high. Did my timing and cams and it didn't help. Changed the ECU with my friend's factory one and it actually got worse so I changed it back.
I'm hella stuck and don't know what the issue is or how to fix. Can anyone point me in the right direction?
Read more: Honda Problems, Ridiculous Idle?
