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Slow/no return to idle
pewe - 20/9/21 at 09:20 AM

Since cranking up the idle speed to pass MOT (as you do) the tickover on my Mk1 1.6 has been reluctant to return to idle even when hot.
It sits at something like 1500 - 2k revs and very occasionally drops down to 950 as set by the idle control screw.
Last time I checked the ICV was working OK when hot.
Any helpful suggestions appreciated.
Cheers, Pewe

HowardB - 20/9/21 at 10:58 AM

sticky throttle cable or a weak return spring?

coyoteboy - 20/9/21 at 11:38 AM

If you have an ICV, how did you adjust the idle speed? The ECU should always keep the idle at factory spec even if you adjust the throttle bypass.

adithorp - 20/9/21 at 01:49 PM

First stop would be to clean the throttle/butterfly and ICV with carb cleaner.
Are you sure you wound the throttle stop back to where it was. As said the ICV would be trying to compensate both when you speeded it up and when you slowed it down. You need to get that stop set right.

pewe - 27/9/21 at 12:56 PM

I think I've cracked it (with your help guys -ta).
Cleaned the throttle body and was then able to re-adjust the idle control screw.
Also reset the TPS so it actually contacts at fully open and fully closed.
I know you can use a BMW 3 series TPS which is progressive but does this need the stand-alone ECU re-mapped to benefit or is it plug and play?
Cheers, Pewe

indykid - 27/9/21 at 06:57 PM

Did you bridge GND and TEN in the diagnostic socket when you were setting the idle speed with the screw?

The ECU will try to compensate for the idle screw adjustment with the IACV otherwise.

pewe - 29/9/21 at 10:48 AM

quote:
Originally posted by indykid
Did you bridge GND and TEN in the diagnostic socket when you were setting the idle speed with the screw?

The ECU will try to compensate for the idle screw adjustment with the IACV otherwise.


No I didn't but it seems to be returning to idle quite well now.
I may just try bridging to see if it makes a difference - still a bit slow throttling back when foots off the accelerator during gear changes so thanks for the tip
Cheers, Pewe

indykid - 29/9/21 at 01:08 PM

Bridge it while you make the idle adjustment and then remove once set