question for the M20 gurus

[M20Turbo]

my friends 89 525i is having a idle issue where it idles like ****. his mechanic said it was the idle control valve. im pretty familiar with the M20 as I have had a 90 325i.

he ordered one from bavarian auto recycling and they sent the wrong one, the one they sent was for an M50.

either way whenevber i pulled the ICV connector off the idle would get worse and whenever i plugged it back in the idle got better. is this normal or is the car supposed to stall?

i told him to send it back and have them send him the correct one since he already paid for it. but upon further inspection the breather hose has a nice crack in it as do the hoses that connect the ICV. are there any other places to check? my theory is that the ICV is still good and there is a vaccum leak somewhere that has to be discovered. the M20 sure looks small in the E34's engine bay. or im just used to seeing an M60 in mine.

Markus, l am having similar issue, my M20 is idling to fast (1200 to1450rpm). I have taken every hose and clamp off along with the Idle Control Value, throttle body & Air Flow Sensor and used carb cleaner. Put everything back and no change. Checked the air flow sensor per the Bentley manual, 5 volts on terminal 3. I connected ohmmeter across terminals 2 & 3, moving the flap throughout its range, the resistance changed steadily. So I assume all is well with the Air Flow Sensor.

Now to test the Idle Control Value, according to Bentley "If the valve is not buzzing with the engine running, or if the idle decreases when the A/C is turned on or shift the car into drive, then you are to disconnect the harness connector and check for resistance on the valve across the terminals. (1 and 2 = 20 ohms give or take 2 ohms, same for 2 and 3, 1 and 3 = 40 ohms give or take 4 ohms) 1 and 2, 2 and 3 checked out okay, but at terminals 1 and 3 I only had 29-31 ohms instead of 40 ohms??

I performed the stomp test and I got Code 1215 Air flow/air mass sensor. The code 1215 would just repeat over and over again. Tried to clear codes but no luck....

What next? I guess I will try ICV tomorrow, is that what YOU would do. Any help would be greatly appreciated.

Installed new ICV, the idle is fixed.......