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Model specific boards => Golf mk2 => Topic started by: Mart8V on 16 October 2013, 09:55

Title: Erratic idle when cold
Post by: Mart8V on 16 October 2013, 09:55

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

Title: Re: Erratic idle when cold
Post by: oakgreener on 16 October 2013, 13:57

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

Title: Re: Erratic idle when cold
Post by: Mart8V on 16 October 2013, 21:56

Thanks.  Nothing obvious thus far but will look again.

Title: Re: Erratic idle when cold
Post by: Mart8V on 24 October 2013, 16:31

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???

Title: Re: Erratic idle when cold
Post by: dragonfly on 24 October 2013, 20:01

Check for air leaks.

Title: Re: Erratic idle when cold
Post by: Mart8V on 26 October 2013, 09:15

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?

Title: Re: Erratic idle when cold
Post by: weazgti on 26 October 2013, 09:51

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.

Title: Re: Erratic idle when cold
Post by: Mart8V on 26 October 2013, 10:32

Quote from: weazgti on 26 October 2013, 09:51

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.

Title: Re: Erratic idle when cold
Post by: bavmk2 on 27 October 2013, 00:34

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

Title: Re: Erratic idle when cold
Post by: Mart8V on 27 October 2013, 11:26

Welcome to my world!

Title: Re: Erratic idle when cold
Post by: Sgt_Lemon on 27 October 2013, 12:49

Are people telling me my car isn't meant to idle like a piece of sh!t?

Title: Re: Erratic idle when cold
Post by: bavmk2 on 27 October 2013, 19:49

Any Outcomes yet buddy?

I will be having a look at the car tomorrow

Title: Re: Erratic idle when cold
Post by: Mart8V on 29 October 2013, 20:55

Quote from: bavmk2 on 27 October 2013, 19:49

Any Outcomes yet buddy?

I will be having a look at the car tomorrow

After some tinkering with the throttle screw and a damn good run up the dual carriageway things have settled a great deal.  Still not perfect but much better!