Erratic idle when cold

[Mart8V]

Hi All,

Back in the game after a few years away from Mk2s!  Have bought an 87 Digi which is in pretty good nick but am having a few issues with the idle.  All temp sensors replaced, dizzy cap and rotor arm done as well.

When cold it varies between 600-2000rpm (up and down) but as soon as the accelerator is pressed the idle smoothes out.  Not an issue when the engine is warm, although there is a slight flat spot at about 2800-3500rpm under acceleration.

It has had the CO and mix done by a local mechanic who knows his way around a PB unit for the MoT. Before I take this back to him are there any suggestions?

Thanks,
Martin

[oakgreener]

Try the throttle body switches for broken wires or switch failure for starters

[Mart8V]

Thanks.  Nothing obvious thus far but will look again.

[Mart8V]

Right- just cleaned out the ISV and reset the idle when nice and warm but still hunting between 600-2000rpm.  Can't find anything obvious???

[dragonfly]

Check for air leaks.

[Mart8V]

No obvious ones.  Have gently waved an unlit gas torch all round the throttle body and vac pipes but no change in revs. 

ECU or throttle switches?

[weazgti]

I had similar symptoms and it was the ignition module on the ecu.
Unscrewed it with it running and moved away from the ecu and it ran sweet. Could hear the leads crackling sometimes and there was a huge flat spot above 2500rpm. I think I nudged the ecu one day whilst trying to find theproblem and the engine ran better.

[Mart8V]

I had similar symptoms and it was the ignition module on the ecu.
Unscrewed it with it running and moved away from the ecu and it ran sweet. Could hear the leads crackling sometimes and there was a huge flat spot above 2500rpm. I think I nudged the ecu one day whilst trying to find theproblem and the engine ran better.

Interesting! Will have a scan tmrw night when I have some time. Will also take off the inlet pipes and get some carb cleaner into the throttle body as the idle screw was pretty grubby when I took it out the other day.

[bavmk2]

I have just purchased a 8v 88 and just had the car delivered, took the car of the trailer and started it up and the car starts up on the key but idles on cold at 2500 - 3500rpm,  once warm I mean half gauge it drops back down but whilst taking it for a quick spin and coming back to a stand still the revs fly back from 950 all the way to 2500 - 3500rpm......,

Anyone know what it could be?

It seemed to be over heating a little aswell

[Mart8V]

Welcome to my world!