Idle problems

[cowden_12]

I have a 84 318i (Yeah I Know) with 106k on it. Anyhow what is this rediculous idle that it has when after it warms up it goes up and down, up and down (at stop lights it is real annoying) and why is it caused?

[KenC]

Have you cleaned your idle control valve lately? It might be the idle control unit as well. Which rpm range does it fluctuate around?

[EtaSport]

Are you ready for this?

(not sure if all apply to m10)
ICV
AFM
o2 sensor
Fuel pressure regulator
TPS
air boot
gaskets/intake/tb
distributor/wires/plugs
coolant temperature sensor
Cold start/thermo time
ECU

check em all. Probably ICV problem, but I replaced everything under the sun to discover my idle problem was from a faulty coolant temp sensor. Also, those air boots get cracks in them easily and cause bad idle problems too.

[zandi]

I'm betting your Idle control valve is dirty, had the same problem, I'd put my car into neutral at stoplights(when i had my automatic)

Your more detailed answer: http://www.r3vlimited.com/phpBB2/viewtopic.php?t=18327

[cowden_12]

I'll check on the RPMs. Thanks guys I will get on it and let you know. Didn't think about the ICV.

[cowden_12]

The idle goes from 1k to 1500 and back down, up, down etc.

[Brew]

Re: Idle problems

after it warms up

Check your O2 sensor before you touch anything else.

[88325isboy]

u might want to check the control unit of it is a vaccum leak.

[nah325i]

the easiest way to "check" some of the above stuff is just to unplug it with the car running and observe changes, if it is the ICV, then the fluctuation should stop or change with it unpluged, same for the 02 sensor. It will not run however with the temp sensor unplugged, and often will not run above idle with the afm unplugged. Take some carb cleaner and spray it around vacuum lines, gaskets, etc to check for intake leaks, if you find one the engine speed will change.

[bichmgnt]

the easiest way to "check" some of the above stuff is just to unplug it with the car running and observe changes, if it is the ICV, then the fluctuation should stop or change with it unpluged, same for the 02 sensor.

Wouldn't the sysmptoms stay the same if the problem was the ICV and you then unplugged it?

I had a broken wire at the plug to the idle control computer that caused this problem.

It will not run however with the temp sensor unplugged, and often will not run above idle with the afm unplugged. Take some carb cleaner and spray it around vacuum lines, gaskets, etc to check for intake leaks, if you find one the engine speed will change.

Check the intake boot for cracks and leaks. It's a common failure.

Good luck.

Steve