03/1987 325is Eratic Idle only at OP Temp that throws a code

[paynemw]

1. Smoke test complete, no vacuum leaks
2. I have a new Bosch O2 sensor in
3. I have a new Bosch CPS with the appropriate gap to the harmonic balancer
4. I have a rebuilt and tested AFM from BavRest
5. I have a new fuel tank, with functional primer pump and main pump, new filter and functional regulators
6. Rebuilt and flow tested injectors
7. NGK spark plugs properly gapped
8. Valve's properly gapped
9. all engine ground straps
10. replaced coolant temperature sensor with newer from another car
11. a 173 DME in an originally Auto car, stomp test won't display codes
12. SPECE30 built engine

I think it's the signals from the DME to the ICV. It totally feels like a signal issue because it's NOT a consistent searching idle issue like a dirty ICV - does anyone have guidance for inspecting harnesses? I have the pin-out for the DME, did you just measure resistance even though it's not a constant break?!

[paynemw]

Update

I replaced the Throttle Position Sensor, it tested within range. I set the throttle plate and the set screw to the proper settings per the Bentley manual. I also cleaned the ICV more. The ICV tested within range during the bench test, however, when the conducting the test connected to the engine harness, the "door" inside the ICV closed completely instead of half way open as per Bentley when the engine is at operating temperature.

The idle is now back to like 600-700RPM. And it dies from time to time, but it isn't eratic like it used to be. AND it throws a code.

I have a 173 DME and the car was originally an automatic. However, when attempting to do the stomp test, I can't get any response from the DME at the Check Engine light on the cluster.

[paynemw]

I finally got the stomp test to work, naturally new TPS correlates with functional stomp test. My stomp test produces code 1444. No faults right?! So

Idle is at 700-ish RPMs when cold, but the car after running for a long period of time now dies after idling at 500 RPM or below.

I've DONE EVERYTHING. I feel like I have a harness issue. My buddy is building his own harness, and I'm on the search for one, but finding a decent M1.1 harness is not easy.

More to come.

[SteveO]

I had some rough bouncing idle problems that im pretty sure ended up being something wrong with the 153 ecu (video here https://youtu.be/R0o6U7TPOZY)

as it stopped after switching out with another 153. Shortly after that when idling it did some weird stuff where the idle dropped down from a 750ish rpm to a high 450-500 rpm and then back up to 750. Then a couple days later it idled at 700 cold and just under 500 when warm. Now swapped out to a 173 ecu for other reasons and it does the same thing... ive just been driving it like this for a year now as its not really been a big deal and haven't been too worried about fixing it, but would be nice to know whats up with it. This post is really of no help to you but here to see what ends up being the solution to your problem