High idle after M52 swap - no perceived vacuum leak

[fdourado]

Hi all, I could really use some help chasing this issue down as its been annoying me for a long time.

I have an M52 swapped e30 with a built motor and lowered compression for future turbo aspirations in my 318is. The car has about a 2K idle when it first starts up and I've replaced everything at this point except the CCV. I have a smoke producing device I use for checking vacuum leaks and can't seem to find any leaks.

Now here's the interesting thing, when I unplug the ICV (which I have also replaced) I can get idle down to about 1K which is how I drive around now. So somehow, the ECU is telling the ICV to open up rather than clamp down on cold start. Mind you I haven't looked into how the ICV actually works, I know the connect has 3 wires but unsure what they do at the moment and

Here are some current theories:
- Might the ECU tune with the lowered compression be causing an issue? I have an MS3 Pro I plan on using in the future but I wanted to get the car running well before I started the turbo transition.
- Maybe something with the plug-and-play harness adapter I purchased is incorrect?
- Maybe the CCV internals are borked?

Any theories/suggestions welcome!

Thanks!

[Panici]

Your idle drops when you remove your ICV and block the corresponding hose?

The only path for idle air in that case is through the throttle body.


Is the throttle body closing all the way to it's stop? Pull off the intake hose and check.