M42 idle issue. help!

[BlueBMW]

Its possibly your cat might be stopped up.  My car currently has no cat, but I cant stand the smell when I get out of the car (smells like an old chevy or something)  Seems like you can get a universal fit catalytic converter for about $70.

[iamcreepingdeath]

ok dudes I have an update.

I went to a junkyard, found a stripped M42 sitting in the dirt next to a gutted 1991 318i, and the ICV was still dangling there on a severed hose, so I swiped it, paid about $8 for it on the front desk, slapped it in my 318is, and BAM!  issue resolved!  it now starts flawlessly without a single shudder on brutal sub-zero mornings!  

So easy!  it just needed another ICV.  I have just been too lazy/broke to buy one, but $8 is hard to beat!  the junkyard btw is upullandpay.com.  check it out.

[dkbmxer002]

hmm i have the exact same issue as you but along with it my gauge won't work. i am thinking i have the same issue, can you post a picture of the icv? i am about to clean it if i find it and i guess maybe my temp sensor is bad so i am gonna try and swap one from another motor because they appear to have the same part #

[Frank Gallegos]

told ya

[longtallsally]

This is a good thread.  I've not worked my way to the motor- yet- in my restoration, but I get this from time to time.

191k on the clock, and perfect starts and everything no matter the temp outside.  However, if I use the AC, drive for a while, shut the car down for even a few minutes, it starts right up, but idles like total crap for a few seconds.  I am very particular about shutting off the radio and HVAC prior to shutting down the motor.

I have thought I just have an intake leak somewhere, but I also think I might have a sticky (despite being brand friggin' new) AC compressor clutch.  My O2 sensor is more or less in spec.

Nothing really to add, but I wanted to mention a couple things for someone searching on this issue.

[colin86325]

I think the M42 uses a stepper motor ICV vs the earlier Motronic units that use a plunger style system. When powered down typically the stepper remains in its last position, whereas the plungers return to the position of least pressure.

[longtallsally]

I think the M42 uses a stepper motor ICV vs the earlier Motronic units that use a plunger style system. When powered down typically the stepper remains in its last position, whereas the plungers return to the position of least pressure.

Makes sense.  So in other words, nothing I can do?

[Hodge]

I believe my ICV is fried as well. I did work on the E36 a few days ago and when I was done the idle was horrid. I tried cleaning the ICV out again today but to no such luck with the idle.

I took the screw for the throttle plate out and happened to have a screw that was the same only longer so I screwed it in and set the idle to about 950rpm with the A/C on. With A/C on before it was about 450rpm and if I gave it gas it would die if I let the throttle pedal out.

Without A/C the idle is about 1000rpm which is where I have wanted it for awhile anyway. I get alot of flywheel/clutch chatter(especially with A/C) and at that idle speed there is virtually none.

I figured it was the ICV because the engine would rev and run perfectly fine otherwise. If I was driving with A/C on and let off the gas the engine would die (clutch disengaged). It would bog to about 450rpm without the A/C.