golf MK3 - low idle at cold start

[noho]

hello, would really be grateful if any members could shed light on this. My trusty 1996 1.8 GL (80,000mls) recently started as per normal but then after a couple of mins approx revs would suddenly drop momentarily to around 500rpm before something told the engine to compensate and it would swing back up to around 1200rpm. This see-sawing would also continue in fairly regular pattern with momentary losses of power when driving. Took into reliable garage (not VW) who diagnosed faulty idle speed actuator and replaced. The original problem has now gone completely however now when it starts from cold it idles very low on the verge of stalling at around 450. It needs nursing with accelerator until it warms up when it purrs perfectly at around 900 RPM.
Slightly concerned that in fixing the main problem it has created another smaller one! Any thoughts as to what logic lies behind this chain of events MUCH appreciated. Thanks

[thefoolmccool]

Try and see if the idle speed acuator has any adjustment on it. What may have happened is that when they changed it, they set it up when the car was warm. But when cold it may not be set right.

It may just be a simple case of tightening a cable or something. Had to do this on a MK3 diesel (completrely different engine) but maybe similarities

[VR5_Lee]

Had the same slow, fast, slow, fast, compensating issue on 1.6 GL / CL (...still don't know which)

It turned out to be a build up of crap, left-overs from the oil breather pipe deposited in and around the mixture 'valve',
If you look at the engine with your knees touching the bumper,
Locate the inlet manifold (middle-back),
Locate big black pipe (don't think it's rubber) comes out to the left and curls round and down to your air filter.

Remove the inlet end of the big pipe and you're likely to see the build up which prevents the mixture 'valve' (still don't know a better word for it) from moving freely - get in there with some good cleaning fluid and a few cotton buds to make sure you get the lot.
Tip: Be careful with the pipes which restrict movement of the 'big pipe' to avoid ripping - this worked out to be an unnecessary cost.
Cheers
Lee

[noho]

thanks for input guys.
I'm wondering if this low rev problem when cold is due to faulty temp sensor simply not sending signal to ecu. My only doubt is it was clearly working fine before idle speed actuator was fitted so makes me wonder why it should suddenly choose to go on blink?

Is it an easy diy job to replace?

[VR5_Lee]

I've left a couple of messages over the past few days so can't remember if I've mentioned this before but;

Check the pipes which allow warm air into your mixture chambers...
When I 'cleaned' the mixture ?valve? I ended up tearing the 'oil breather pipe' and a short ?hot air? pipe which seriously effected the way the car ran.

locate Inlet manifold - Back middle,
locate 'Big Pipe' - Goes off to the left from inlet manifold and down to air filter on left,
check pipes coming off 'big pipe', one's about 2 1/5" long and 1/2" Diameter (this was blocked on mine), the other goes straight down (forward) in the car (this was torn, big hole).

The lack of hot air 'breathing' from the engine being re-used in the system could be the reason your car thinks it's colder / hotter than it is and compensates by droping / rising revs.
Quick to check and cheap to replace.
Cheers
Lee