I have a pretty simple question but I haven't been able to find an answer in any threads. Probably because it is over simple. So I have a 1990 740 non turbo. I recently replaced the cps sensor, cleaned throttle body, air filter, regular tune up stuff. The idle was a little bit high so I adjusted the little red screw that tightens, loosens the throttle cable. Everything I have been reading has said that my cars idle is set automatically. Am I harming it by adjusting it manually?

 

I have it at about 600 rpm now and it seems to be running great

 

If the cable was too tight and causing the throttle body to stay open a bit, then adjusting it is the right thing to do. Basically once the throttle plate is closed, the throttle position sensor should switch in the idle circuit and the computer then controls the idle via the idle air controller.

600 RPM is what it is supposed to be so it sounds like you did it up right.

 

Awesome thanks so much! This morning i thought it was even idling a little bit to low but what you said makes perfect sense. With the cable loosened up the throttle sensor is controlling it properly.

 

the correct way of adjusting it is to first ensure the throttle cable is slightly slack at idle, and the throttle position idle switch is closed, and opens almost as soon as you give it even a hair of throttle.

Now, block the IAC via hose pinchers when the car is fully warmed up, in park or neutral, and all accessories are switched off (AC, headlights, ventilation fan, stereo) and it should idle around 500RPM, almost on the edge of stalling. unblocking the IAC hose and it should idle at a steady 600rpm regardless of a/c or accessories. When the AC compressor kicks on, its pretty normal for the idle to hesitate for a blink then recover. ditto when you shift into gear with your foot on the brake.

See Throttle Body and Throttle Position Switch Adjustment it the 7XX/9XX FAQ...

 

Thanks again Pierce very helpful! I will get into this once i get off work and see how it goes. I played with it a little bit before i went to lunch and it's idling at 800 now pretty consistently.