ICV - nothing happens when I unplug it!

[SpecM]

Did you test\check the ICV computer (relay) green in color under the glove box?

he has a '90 325i. so no ICM

[aberg83]

Bumping this back up. I'm chasing a very similar issue. Was this ever resolved?

[Thizzelle]

same thing for me, I can't figure this shit out.

[603Racing]

Bumping again because i have a similar thread going. Were there any resolutions to these problems?

[E30NJ]

Check the breather hose from valve cover to throttle body for orange gunk and replace it if necessary.

[Z3C Tblau]

Bringing it back from the dead...

Same issue here, '89 325ix touring, 173 ECM.

I'm in this sad state of 'TB cracked open' in order to get a 'functioning' cold start after plugging my 'last' vacuum leak (evap hose fitting on the throttle body is now plugged)

And after following jlevie list of potential culprits (thanks!), it looks like that previous leak was hiding a malfunctioning ICV system :
While plugging the leak I also reset the butterfly position (to approximately not on the end of its course, using light as a mean of evaluation...), then set the TPS. It worked fine on the next engine start as it had been run a couple hours earlier, but after driving a bit and feeling that the revs were not going back down quick enough in certain situations, I backed the stop screw a bit (or two).
Evidently, the next morning, no smooth running, rather sputtering and quick death... setting the throttle stop so as to get a decent cold start is the fix to drive to work tomorrow, but isn't really satisfactory...

ICV itself is alright, moves freely, measures OK and the vane operates when alternating voltage on pins 2-1 then 2-3.

But voltage at its pins and vane position with engine hot and ignition ON are incorrect with regards to what the book says : position is closed, and voltage on one side is 9.7VDC while the other is 4VDC (engine hot or cold).
In fact voltage on ICV connector while ignition ON are (with regards to GND) : 18 - 27 - 6 V AC (or 2.8 - 12.5 - 8.5 VDC)
If you couldn't tell so far, I don't understand 3 phases motor control...

On that note, I'm not sure I understand Nando's following quote (post #7 of this thread):
"the only thing I can think of is the ICV is gummed up and not able to open past about 25% DC (~35% is about where warmup would be, ~50% is cranking DC, ~15% is closed)"

Quite sure DC in this context is duty-cycle, but....

Also, it looked as if the DMM would read the same 9.xVDC for a very brief moment before going down to 4V, as if someting was in a bad shape in the ECM... Opened it up, and haven't found anything of interest.

TL;DR : bad cold start is bad. Any help would be appreciated.

[laidback93]

Keeping this thread alive as I've been experiencing the same issue for quite a long time with no fix so far. 1990 325is.

I have the same issue where unplugging the ICV has no effect on cold engine idle. Cold idling is a big problem of my M20. The idle will start surging for a good couple of minutes of running. Sometimes I have to keep my foot on the throttle so the revs don't drop too far and it stalls out. Once it's at normal op temp, it idles beautifully.

I've done/checked just about everything in this thread. Multiple folks have tried to figure it out over the years to no avail.

[tomstin]

This is for the E models but may give you some ideas https://www.verrill.com/car/e30_idlefaq.shtml

If all else fails, near the bottom of the article, try "Idle Kludging"

Good luck

[Z3C Tblau]

Problem solved!
Bought a more recent ECU (525 instead of 173) off ebay
I read a quote somewhere from a magazine or something stating that 320 and higher versions of our ECU were less prone to this bullshit...
The output stage is different for sure from my old one (different impedance between the two versions)

The morning after I received the newer ECU the ICV started working again : I really thought I had a new leak but disconnecting the ICV made the rpm change (down).
It worked for one cold start + 20km. Next start, it wasn't operating anymore : had a high 900rpm before shutting it off, then an hour later it was high 800rpm, as usual these last few weeks)
Thought it was a wire harness problem, but after controlling it again more thoroughly (twisting it at the ECU plug), it looks as if the ECU sensed it was gonna be put down and tried its best one last time
It wouldn't perform the next morning, so I installed the newer ECU after checking it wasn't shorted (you never know...)
On cold start the rpm were around 1200 (linked to the screwed open throttle, and as the previous morning)
Checked that it was really ok (and not a fluke related to a new leak) by returning the throttle to the closed position and adjusting the throttle position sensor, cranking the motor then disconnecting the ICV 30s after cold start --> idle dropped. reconnected the ICV --> idle back up to 900rpm then going down

Also notable : ICV voltages are not different than previously (while ignition is ON, 4V on one side 9.5V on the other, haven't checked while in run).
Seeing as most people with this same problem read these same voltages, is it possible that the Bentley is describing an older version?