Ok I checked MY BAC with a ohm meter/voltameter and it reads ok

I heard that they can stick and cause your car to idle very low or not idle at all (but this is an extremely rare case)



so my questions are:

how do I clean a bac valve should I spray with a degreaser or wd-40?



what does TPS mean?



can a bad O2 sensor cause no idle?



I've started to replace the vacuum hoses around and bottom of the intake manifoild but I'm not still getting a idle. Anything else I should keep a eye for? I'll order some more hoses today!



Today a friend is coming over so I'm going to adjust my throttle cable and hope that is the source of my problems!



I recently heard not you should NEVER play with the throttle screw ( I'm almost certain this is a lie!)

I can't belive what some Mechanics tell me



86 GXL

 

Download a Factory Service Manual or search the forums for how to properly adjust the TPS (throttle position sensor) there are a few very good write-ups as it is a common problem. The TPS itself is the small black "plunger" looking sensor connected to the Throttle Body near the throttle cable.



as for the idle adjust screws and whatever....it's an 86...not like youre gonna void a warranty or something .



kevin.

 

play with the idle screw all you want, it just sets the amount of air the engine gets at idle. the fuel adjustment is down by the airbox, dont touch that yet, that def isnt your problem. generally a vac leak is the root of idling problems, i dont know about the 02 sensor. oh, and TPS stands for Throttle Position Sensor... in the S4's its basically just a switch that is supposed to say "no throttle" or "gas is pushed"... doesnt have any sort of analog readout, and is pretty straightforward to adjust, just make sure its working. a quick search will show you how to.

 

there are 3 screws on the throttle body. 1 is the idle speed screw, play with that all you want, second is the throttle position sensor screw, play with that too. there is a 3rd one that adjusts where the throttle plates stop, this you shouldnt have to touch. if you play with this it confuses the computer.



o2 sensor shouldnt affect idle, except to throw off the mixture a bit, if its bad



the bac valve plunger should move when you apply 12v and a ground to it. brake clean/carb clean works best. if it doesnt move its bad



the tps being adjusted right, the car basically runs from that under 27% throttle



other misc, make sure the intake gasket isnt blown, they do that, and it wont idle if it blown

 

When my O2 sensor was bad, it caused the car to run too rich. I could tell by the black deposits all over the rear bumper. Didn't affect idle though



To clean the BAC valve, take it off and flush carb cleaner through it. Apply a 12 V source to it and you should hear a distinct click and see the plunger move.



Vac leaks are most likely a cracked or loosely fitting hose. Obviously, check the hoses first. Vac leaks can also occur at the UIM and LIM when the gaskets are worn out or torn. Vac leaks can also happen at the injectors when the lower grommets and O-rings are worn out or not seated properly.



Set the TPS to 1000 Ohms, engine fully warmed up and turned off. Once that is done, ground the initial set connector, or short it depending on your model, and set the idle speed to 750 by adjusting the screw on top of the throttle body.



Unfortunately, there's no magic button to push that will cure idle problems. Looking through these forums, you'll see that the most common ailment in these cars is idle problems. You have to be methodical and eliminate possible causes one by one.



...good luck