Proper throttle adjusting

[shay91]

I have a 1988 325i convertible manual trans with a few kinks I'm trying to work out, I've read through the Bentley manual and I'm still a little stumped. What is the proper way to adjust the TPS and idle speed. If I'm not mistaken my idle speed should be 760+/-40 but I can't seem to get the idle down. If anyone can give me a simple how to on this that'd be great.

[bmwstephen]

Automatic trans?

[shay91]

manual sorry.. updated

[whodwho]

Make sure someone hasn't adjusted the throttle body stop to raise the idle. The throttle plate should be fully shut and the stop adjusted till it just barely tries to open it. The TPS should click just coming off the throttle stop when opening the throttle.

Somebody recently had an idle issue and there was something holding it up from returning. Make sure the cables aren't over adjusted and the cruise control cable is hanging up.

Idle idle speed is computer controlled and using ICV, make sure it moves freely inside. You should be able to rotate the ICV back and forth and hear/feel it move. Make sure there are no vacuum leaks as those can increase idle speed.

[jlevie]

With the engine at normal operating temperature, disconnect the ICV and adjust the throttle stop for an idle of 900 rpm. Then adjust the TPS so that the idle switch closes whr the throttle arm is 0.030-0.060" off the stop screw. When the is reconnected the idle should stabilize at 750rpm.

This presumes that the throttle body, acclerator cable, and cruise control cable aren't binding. That the ICV isn't sticking and that there are no intake leaks.

[whodwho]

With the engine at normal operating temperature, disconnect the ICV and adjust the throttle stop for an idle of 900 rpm. Then adjust the TPS so that the idle switch closes whr the throttle arm is 0.030-0.060" off the stop screw. When the is reconnected the idle should stabilize at 750rpm...

Wouldn't adjusting the throttle stop for 900 rpm keep the idle at a minimum of 900? How would it be able to come down to 750??

[jlevie]

The ICV will go wide open when disconnected. So you are setting the upper limit of the throttle with the stop screw and the DME will reduce air flow via the ICV to achieve correct idle.