Fast idle only once up to operating temp. Yes I searched

[fastbub]

Ok so it is an 86 325 es. I don't think it is a vacuum leak problem. No it has not been smoked but symptoms don't seem consistent with a vacuum leak.

Cold starts great. Even on the 15 degree days we have had this past week. Starts right up with a rock steady idle at like 700 rpm. Idles at this speed all the way up until it gets to about 185 (operating temp according to my VDO temp gauge). Once it is up to operating temp it prefers to idle at 1200. It is not a rough idle or surging or anything weird. Just high. If I unplug the ICV it goes up higher, so I assume the idle control magic box is doing SOMETHING. I took off the valve and it seems free. Rattles when you shake it. Where do I go from here? It is very consistent with this and steady so that's why I am not thinking vacuum leak. Does the thermo time switch play a part here?

[e30davie]

VAC leaks do all kinds of weird things, id just check all the hoses and clamps at least.

Also attack your ICV with some Carby cleaner. See if it makes any difference.

[tim88325is]

Small chance but have made sure your throttle linkage is adjusted correctly?

I had my linkage hang up and cause a high idle once...

[ahlem]

Make sure your AFM is swinging all the way. What happens when you unplug it?
Check your power brake booster hose by unplugging it and blocking it off. Did you do any adjusting to the ICV at all?

[ahlem]

I only have experience on an M20B25 but are your temp sensors clean and testing correctly? And hooked up correctly?

[fastbub]

Make sure your AFM is swinging all the way. What happens when you unplug it?
Check your power brake booster hose by unplugging it and blocking it off. Did you do any adjusting to the ICV at all?

I did try and adjust the ICV and it is dialed all the way in. Backing it out speeds up the idle. Checked the brake booster as well.

[fastbub]

I am still leaning towards something related to operating temperature. The idle is perfect, steady and smooth at around 700 from a cold start all the way up to operating temperature. Then it is high. Between 1100 and 1200 but still smooth and steady. But only once it gets up to temperature.

[95BMWIC]

I am still leaning towards something related to operating temperature. The idle is perfect, steady and smooth at around 700 from a cold start all the way up to operating temperature. Then it is high. Between 1100 and 1200 but still smooth and steady. But only once it gets up to temperature.

Could be the coolant temp switch and coolant temp sensor..

I pulled the Bentley manual..

Did you test the resistance on the Idle air Stabilizer valve? 40 ohms of resistance between the two outer terminals and 20ohms between the center terminal and the outers.

If this is within spec - the next thing is to check the signal from the ECU in the wiring harness with an Ammeter - The plug on the 2 pronge valve should fluctuate between 400 - 500 mA.. With engine at operating temp..

If you have the 3 wire valve then use a voltmeter to check. With the ignition on, there should be battery voltage between the center terminal and a ground (12 VDC) and then from center to the outer pins it should be 10 VDC.

If your not finding any electrical faults - it could be the ECU. You could try "resetting" it by unplugging it and replugging it in a little while later.