okay i have a few questions in regards to the operation of the bac valve and cold idle. if my understanding is correct the bac valve does cold idle compensation and some load compensation. my car idles quite odd while cold. the first time i start it in the morning it does the hunting for idle crap. ive done a pressure test on the intake plumbing and @ 10 psi found no leaks. now it gets wierder, if i modulate the clutch pedal from fully depress to just before engaged and hold it the idle will straighten out. i can then let the clutch out in neutral and it will most of the time idle fine and steady. i have also found that if i reduce the fuel at idle it will stop hunting and backfiring. but it only does this when it is cold. i have removed the rats nest and thermowax from throttle body. the air supply valve and bac valve are the only things still on it. i have been debating replacing the bac valve with another one i have but just havent done it yet. oh yeah with it is hunting for idle the bac adjustment screw doesnt do squat for adjustment. anyone with any ideas?

 

Have you tried setting your TPS? Lots of threads on how to do it. Hunting idle is a typical symptom of a TPS that's out of whack.

B

 

Set your TPS and idle according to the FSM. If it still hunts... it's probably your BAC. While it's hunting... unplug the BAC electrical connector and see if it rids your problem. This is what mine was doing and I recently just unplugged the BAC, for now.

Josh