Alright, so I have a '90 SI hatch with a B18b1 out of a 97 teg. Recently the car's rpms would drop to 0 if I put the clutch in and then it would stall out. Did some searching and figured it might the the IACV, so I took it off, there was some black soot looking stuff on the screen thing for the two hole. Got it all out, sprayed the inside with brake cleaner and put it back on. Now the car doesn't die or anything and it idles around 770RPM's now, but when I have both my headlights and heat on, it idles around 450RPM's. I've changed the ground for the headlights, and ground for my battery but didn't seem to help. So is this normal for the RPM's to drop? And if so should they drop that much?

 

I am dealing with a DA b18 in a crx si with pretty much the same problem.. jumpy idle after it is warm. generally idles around 800 rpm, but it will drop randomly to like 400 and almost sound like it wants to stall. I have done FITV, IACV, and messed with the throttle body idle screw, all for naught.

The last idea I had was that the brake booster was leaking vacuum or causing too high of a vacuum, which was causing the idle to drop. My theory is that the master cylinder was leaking into the brake booster because of the extended period of time the car was down after the owner blew the old engine, but I have yet to test that theory.

Either way, I'll be watching this thread for updates. good luck

 

Come to think of it, my brakes feel spongy. Could that be my issue?

 

well, i have not yet confirmed on this other car.. but it might be worth some investigation.. The brake booster is known to sometimes go bad when the master cylinder starts to leak, the booster diaphragm can't handle the corrosive brake fluid.. so i would definitely not rule it out, but i would probably test it by putting clamping pliers on the hose briefly to see if the idle issue goes away. if you decide to drive it though, just be careful stopping..

 

I drive it daily, not far distances, but it is driven and I take great procautions while braking.