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Engine not returning to idle

Printed From: BMW Car Club Forum
Category: Cars & Registers
Forum Name: M Power
Forum Description: Discussion forum for M Power cars
URL: https://www.bmwccgbforum.co.uk/forum_posts.asp?TID=15973
Printed Date: 18 Apr 2021 at 7:10pm
Software Version: Web Wiz Forums 12.03 - http://www.webwizforums.com


Topic: Engine not returning to idle
Posted By: Robert
Subject: Engine not returning to idle
Date Posted: 12 Sep 2020 at 1:39pm
I have an E30 M3 that is having trouble with the idle control.

When you rev the engine a bit it will then stay at around 2000rpm for about 10 to 15 seconds before settling back down to a slightly higher than it should idle of 1000 to 1100rpm.

I have had the ECU refurbed and replaced the ICV (Idle Control Valve). In all other respects the car is running fine and the economy is good.

If you unplug the ICV when the engine is running and doing it's idle at 2000rpm it will immediately return to idle OK around the 850 to 900rpm mark.

I have also replaced the short section of hose leading from the top of the ICV to the distribution piece where the idle screw is.

Am I right in thinking there is still an air leak somewhere or can it be a poor electric cable?

Rob.



Replies:
Posted By: Robert
Date Posted: 23 Sep 2020 at 9:48am
Can anyone recommend a competent mechanic that is specialized enough with the S14 engine to be able to diagnose the fault with my idle control? I am in the East Midlands but would be quite prepared to travel a greater distance.

Thanks
Rob.


Posted By: Robert
Date Posted: 11 Oct 2020 at 5:30pm
UPDATE

I sprayed the little temp sensor that's in the rear of the AFM again with some air flow cleaner and Bob's Your Uncle, all good.

With the new HT OEM leads fitted and the engine returning to idle when it should the car is a whole new machine. I can't remember when it ran so smoothly and boy, does it like to rev. There's a strong punch in your back at 5,000rpm and again at 6,000rpm. You have to be quick off the throttle to not bounce into the rev limiter. What a joy.





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