1989 TII Idles fine, but almost dies on deceleration.
 

My car idles fine until I give it gas and let off...

As soon as I let off the gas the idles drops down and the car wants to stall. I have tried adjusting the BAC screw but that doesn't have any effect whatsoever.

There are no air intake leaks and this problem ONLY occurs after I let my foot off the pedal. The idles goes down to almost 0 and then almost dies, then returns to a steady 750 RPM.

I am going to work on it tommorow, but what all could cause this? Faulty or dirty BAC? Faulty TPS? Faulty actuator solonoid?

I am not totally sure but try to find out some info on the Dashpot. I think that is a key factor in smooth deceleration.

i would say its the BOV... check it... you may need to retighten the spring setting on the apexi bov..

i just got my car started since storing it for winter and installing BOV..

sounds great... on partial throttle decel, it seems like the BOV will flutter... i adjusted the spring to the max tension possible...

the car will just pop and back fire when i have partial throttle decel...

too bad i have a cat or i would be having some awesome flame show...

too bad my bumper is covered in soot now... =(

anyhow check the BOV.... i'm pretty damned sure it is the apexi BOV u have.

Its obviously the TPS, because when the car starts decellerating, if the tps is faulty its stays on 99%, but if its working then the car will go to 00%, if its faulty and stays at 99% then the car is flooding it self, be careful of this.

or maybe your TID is cracked just a little, causing air to escape?

i'm having the same problem, you can check your BAC, if you can stick your ears to the filter while the engine is one and then UNPLUG THE BAC, you shouldn't hear a deep rumble anymore, meaning your BAC was working.

To check if your BAC is still good, take it out, apply 12v on it, and make sure it CLICKS, if it does then it's working.

Check your ECU -> by checking the volts of the PLUG of the BAC valve, should be around 12v then when headlights or ac come on it should lower at it opens more.

Maybe some BAC cleaning? take it out and blast that biotch with carb cleaner.

i'm having the same problem as of right now, i have no emmissions what so ever, so i can't be a vac leak, did you try the HARD idle SCREW?

http://fc3s-pro.com/TECH/HOWTO/TPS/tps.html
on the bottom.