Can't Figure Out Idle Issues

[Willy73]

Hey guys so I'm new here, mainly because I need to consult some E30 owners with actual experience one the field of problems. I got my 325i from my dad a few months back, it has a Euro 2.3 swap in it, and recently it's been giving me issues that - no matter what I try - still won't be solved.

The problem? When I start it, it automatically revs to 1500, then to 2000, and back down to 1500 where it goes up and down repetitively. Now at first, the car wouldn't even idle unless I gave it gas, which was because the pins on the ICV had been pulled out and were touching each other inside the sheathing. Fixed that, and now this.

I have since tried a brand new Bosch ICV, one of my spares, and a cheap one I had lying around just to see. I replaced the Throttle position sensor, and used my other spare of that, as well as checked the throttle stop screw as well, all is fine. The AFM I swapped my spare in it, and it actually gave me a fault code for a bad AFM and had super low idle, so I went back to my original. I swapped a spare ECU into there out of a 525 E28, and it made no impact on the issues I was having, so I went back to the OEM one.

I've been trying every little thing I can to fix this the past 3 months, and it's been nothing but disappointmemt at its finest, yet I refuse to give up on the legacy of this car. So TYIA for any help.

[MrBurgundy]

TPS sensor,

check that. If there's not idle signal being sent to the ECU, the AFM will be wide open

[Panici]

Vacuum leaks anywhere?
Check all the lines coming from the intake manifold.

[Willy73]

Vacuum leaks anywhere?
Check all the lines coming from the intake manifold.

I did a full leak down check on it this morning with a smoke machine, not a single leak besides for a super small one on the AFM from the intake boot not being on all the way. Fixed that and the idle still isn't steady

[Willy73]

TPS sensor,

check that. If there's not idle signal being sent to the ECU, the AFM will be wide open

All 3 of my TPSs gave the same result. When I put it on I turn it so it clicks, then screw it down, and it clicks again when I just barely move the throttle cable - Is that correct?

[MrBurgundy]

You want to set adjustment with a continuity test.

your middle pin to the left pin should give continuity with the throttle closed. That's your signal the the DME that its time to control idle via the ICV and then once that's set, the WOT position will be giving continuity to the middle pin and right pin when its about 75 percent open.

It clicking should be the switch engaging, so it might be correct, the the real way to test it is like I said above.

But idle should be very simple.

-start with a smoke test
-continuity test of the TPS, verify adjustment
-test continuity at the DME side of the harness to make sure that TPS signal is making it to the DME. This will test the harness.
-then we want to test the harness to the ICV, the ICV plug and the ICV
-after that, throttle stop screw should be set after all the above is working.
-Unplug the working ICV, idle should rise to about 900 rpm with the screw adjusted properly. Unplugging the ICV will have it move to wide open.
-after plugging the ICV back in, the ICV will start to close to the requested idle speed the DME wants.

This is off the top of my head

[Willy73]

You want to set adjustment with a continuity test.

your middle pin to the left pin should give continuity with the throttle closed. That's your signal the the DME that its time to control idle via the ICV and then once that's set, the WOT position will be giving continuity to the middle pin and right pin when its about 75 percent open.

It clicking should be the switch engaging, so it might be correct, the the real way to test it is like I said above.

But idle should be very simple.

-start with a smoke test
-continuity test of the TPS, verify adjustment
-test continuity at the DME side of the harness to make sure that TPS signal is making it to the DME. This will test the harness.
-then we want to test the harness to the ICV, the ICV plug and the ICV
-after that, throttle stop screw should be set after all the above is working.
-Unplug the working ICV, idle should rise to about 900 rpm with the screw adjusted properly. Unplugging the ICV will have it move to wide open.
-after plugging the ICV back in, the ICV will start to close to the requested idle speed the DME wants.

This is off the top of my head

Definitely going to try this when I get the chance off work. On a side note, I did a stop test and got code 1215, people say it's either a bad AFM or a massive air leak? So maybe both my AFMs are bad, there's something going on that went undefeated by the smoke test, or what you said is what fixed all issues

[Willy73]

Okay so update with this whole situation - The ICV was stuck fully open when ignition/engine was on, we traced it back to the ECU and figured out the transistor was smoke checked.

So I ordered a new ECU, just put it in after making sure everything ok it was fine, but now the ICV only works when the air flow meter is unplugged - the idle control valve goes full throttle once the air flow meter is plugged in. Maybe something else in the wiring harness got messed up when the idle control valve wires shorted?

[Northern]

Does it close when you open the AFM Flap? Just makes sense to me that the ICV would open to try to draw more air if the AFM is closed