i set my timing and my tps then i adjusted the bac but every time i adjust the idle speed screw on top the idle kicks up to 1500 rpms and retards the timing by an inch and a half if i adjust it to where the timing is almost to the yellow dot it idles really ruff almost stalling and if i turn the wheel all the way it will stall but if i hit the gas the bac makes the idle go to 1500 again retarding the timing again, man is this confusing.

 

N/A or T2?

are you talking about the idle speed screw on top of the Throttle Body?? I dont believe there is an adjusting screw on the BAC itself

When you set your timing, make SURE that your idle is below 1100; after that point, the ecu advances the timing. I think Hailers had a jpeg of it.

 

When setting the idle speed the initial set coupler is supposed to be jumpered to put the BAC at a set duty cycle. Frankly it's better to remove the BAC plug and then set the idle as close to 750rpm for a idle then reinstall the plug.

The ECU advances the rpm anytime the rpm's are over 1100rpm give or take.

 

i adjusted the idle to 750 with the coupler jumped plugged the bac back in and i still got a ruff idle and when i turn the wheel it still wants to die and if i set the bac any higher the timing get retarded again

 

am i missing something

 

How do you know the timing is getting retarded?

THere's an Air Supply Valve on the back of the throttle body that should respond to power steering inputs. Is it connected up???

The timing gets ADVANCED when the engine speed gets over 1100rpm. B/t 750rpm and 1100 it stays steady at 5ATDC and 20ATDC. Over 1100rpm and it advances.

There is a variable resistor on a series four car. Turn it clockwise to make the mixture richer. It has STOPS on each end. Do not force the screw past the stops or bad things will happen.

 

thats what i meant the rpm go up above 1100 and it retards, maybe the line is to small that i put on there when i took off the the uim maybe i hooked one of those lines backwards, would that make a difference i know your going to say vac leaks could cause this but i sprayed carb cleaner on every thing that might be leaking to se if the idle drops but nothing. Thanx to you hailers im getting somewhere!

 

i cant figure out how to set the mechanical idle, you unplug the bac put in the jumper then screw the screw out on the top of the tb but, what if the screw is allready out how do you get it to where you can i adjust the screw in and then adjust it back out?

 

on the air supply valve there is two vac lines right one closest to tb goes under and to the front of the tb and the other goes right below the air supply valve right? also the one that goes under the tb to the front shoud have a restricter pill on it and it doesnt, would that matter?

 

How do you adjust the mechanical idle higher?
by the way it is an 1988 s4 n/a

 

do you think my air supply valve is bad?