Blowtus

Ok. My car seems to idle slightly low, ie 600rpm or so. I've searched, and I just can't find a decent answer. How do I raise the idle? I can't find the initial set coupler, I don't know how to 'jumper' it, and I can't find the screw on the bac. Theres a deep hole thing on the bac that looks like it could have a screwing thing inside it, but it doesn't. Thanks for any help...

Charlie

J-Rat

iTrader: (2)

Initial set coupler: On the left front corner of the engine bay. I have a pic, but I cant get to it right now.

Jumper: One solid peice of wire with 2 spade connectors at each end. Inserted into both connections of the initial set connectors = Jumpered initial set connector.

Idle can be changed also by the AIR/FUEL mix (NOT THE VARIABLE RESISTOR!). This is located under whats called a "Blind Cap". Its a black rubber cap that sits on top of your TB. Under that is the AF screw.

As far as the BAC, I was unaware that it was adjustable.

Rat

Blowtus

should I notice a difference in idle after fiddling with the mixture screw without the initial set coupler jumpered? I assumed I would, but I didn't... (yes, it's back where it was)
Where would the initial set coupler wire go back to? I've got a few spade connections around the front left side...

Charlie

J-Rat

iTrader: (2)

This is going to require some pictorial assistance. There are 2 connectors in the front left side of the vehicle. One is a big one (i think its green), is the ECU connector. The other one is a 2 plug connector. Thats the initial set. You run a wire from one of the plugs, right back into the same connector, to the other plug. If you were messing around with the Air/Fuel settings without the initial set jumpered, the ECU THEORETICALLY should have tried to compensate for the changes, and return it to the 600 RPM idle you are seeing.

According to the FSM, you set the idle by jumpering the initial set, then adjusting the Variable Resistor, and the Air/Fuel mix (timing helps too). Your idle shouldnt have deteriorated that badly unless you have done something to your motor, or maybe your B.A.C. is acting up. Most of the time, the Variable Resistor is factory set, and doesnt need adjusting unless you get a new motor.

Rat

Are you S4 or S5?

Blowtus

hmmm, cheers rat, this is on an 88 s4 turbo, stock aside from mild exhaust...
could there be anything wrong with the bac causing it to drop my idle? I thought it could only raise it...
I'll see if I can find the coupler tomorrow. Have used the big green ecu one no worries...

Charlie

J-Rat

iTrader: (2)

The BAC will drop your idle if its not compensating for loads to the motor (heater, stereo, etc...) Other then that, something is up...You know that stock idle is 750 right?

Blowtus

yeah, I'm chasing an idle of 750... the bac works, my idle is normal with air con etc on, though it does appear slow to respond. ie my revs dip when I pop up my lights, turn air con on, etc.

Charlie

Remzuo

if there's any kind of draw on the battery when it's idling, you can hear the revs drop. most any electrical system will do that, including foglights/stereo/rear defrost/headlights/AC/blower

BlackRx7

best bet is to get a skilled rotary mechainic to dail out the idle, its pretty hard for the average mechanic, and one word of advice don't mess with the varible resistor, 1 degree of adjustment changes alot.....

J-Rat

iTrader: (2)

I am not afraid of the Variable Resistor!

Rat