So today while working on breaking the engine and auto tunning, my idle suddenly raised to 2500 RPM. I pulled over and checked all the obvious things I could think of and got it back down to 1200-1300 by backing the idle set screw all the way down. I drove it around a parking lot for a bit and it was fine. Then coming to a red light the the car stalled out.

I made sure the trottle was not sticking and the TPS is calibrated and was reading correctly. My only thoughts are that the BAC valve was stuck open, causing the high idle and then closed again while driving? Not sure what else could cause it.

Any other ideas? If my BAC theory is plausible what is my best option, clean it good?

Its an 88 TII with an MS2.


Thanks.

 

My first guess would be a largish vacuum leak. A hose popped off or something.

 

That is what I thought too when it started. I checked all the hoses and didn't find anything and the strange thing is it corrected itself while I was driving causing it to stall. Then when I set the idle higher with the set screw it was fine. I just warmed it up and its idling fine and can be adjusted with the idle set screw as normal. I popped off my BAC and checked it out. It pops open when power is applied like normal.

From what I understand, something has to be bypassing the TB if its idling when the TB is fully close and the set screw is backed all the way out? I will take it back out tomorrow and see if it happens again.