High idle once warm

[BrownHausE30]

First time posting, long time reader!

I have a 325i convertible 1986, owned it for 10 years and love it when it runs right

over the last year I have been chasing a high idle issue, when the car warms and I’ve driven it for more then 30 minutes the idle will sit at 1500rpm

the list of things replaced it’s as follows
-new idle control valve
-rebuilt TB with new seals
-checked and calibrated AFM
-ECU tested by injectronics (Australian ecu repairer)
-New rocker cover with gasket and D seals
-Fuel system rebuild after tank went rusty (new pumps, injectors, reg, filter and lines as well as tank)
-New intake boot
-New intake manifold gaskets
-Converted TPS from 6 to 3 pin and installed new TPS

I’ve also tried blocking off the booster line when the issue occurs with no change

any suggestions are welcome, I am starting to think I have a faulty wiring harness as I’m at a loss to what it might be

(just quickly, I own a workshop and specialise in VAG cars, this old girl is testing me big time)

[tomstin]

A few thoughts, there is a harness connector under the intake manifold that tends to corrode over time. Unplug that and make sure all the pins are clean. Next, I have more experience with the E model, but check the various temperature sensors are reporting resistance back to the ECU correctly. There is a good write up for the E model, not sure on the I models.

[BrownHausE30]

Thanks tomstin, I’ll look for that connector

I have also replaced the temp sensor but thank you for the suggestion

[82eye]

have you done a smoke test on a warm engine?

[It's Soda Not Pop]

The new ICV is it Bosch (OEM) or knock off brand? If so they can cause issues. I have ran into this problem.

[BrownHausE30]

have you done a smoke test on a warm engine?

I did previously hence the new rocker cover gasket and D seals

[BrownHausE30]

The new ICV is it Bosch (OEM) or knock off brand? If so they can cause issues. I have ran into this problem.

it was a Bosch part, sure I purchased it through FCP

[It's Soda Not Pop]

https://www.r3vlimited.com/board/forum/e30-technical-forums/e30-faq-and-diy/333798-diagnostics-tips-tricks-by-jim-levie-e30-jedi-master

[BrownHausE30]

Update

found my ICV connector pins to be spreading when warm causing the erratic idle, squeezed the pins back together and stabilised idle significantly

[BrownHausE30]

Just went on a extended road test, issue resolved

might look into getting a new wiring harness made up

[packratbimmer]

Can you hear an audible click at the throttle switch when returning the throttle to rest? The 325i really enjoys having the throttle plate and switch adjusted properly.