Initial start up - Running rough then fine (1.8GTi/PB)

[KingNine]

Quick question for you experts:

My '90 1.8 GTi (8V/PB engine) 115Kmls - on first start of day runs very roughly and has to be kept running by juggling the throttle to keep the revs at about 13/1500 for about 30secs, then it will idle at about 600rpm OK. Once even slightly warm, it runs & idles perfectly, no hesitation, smooth, free revving.

The usual suspects are fine (connections secure, plugs/HT/dizzy cap clean etc) not that I thought that'd be the issue as it runs fine 99% of time. I've cleaned the ICV although it wasn't dirty (& I did it 6 months back when I serviced it) and replaced the blue temp sensor in case that was giving a false reading, it seems to be slightly better than before but the fault is still there.
Before I go further into it, anyone got any more pointers??? My money would be on another sensor issue related to cold starting as the car runs fine at all other times.

Cheers.

[DarnPB]

It may just need an old fashioned tune up and/or service. If its running a little rich, then that may give you these symptoms. Check the gaps on your spark plugs and service them if necessary. Of no joy, then take a look at Rub Johnnies tune up guide in the hallowed maintenance section.

http://www.golfgtiforum.co.uk/index.php?topic=33253.0 
(To save you looking for it!)

[KingNine]

I've kind of covered that, the mixture (unless someting has 'moved' which is V.unlikey) and the timing etc. are OK as I've checked them already. I've also checked the breathers etc, it seems to be connected with the change in the weather - literally.
However, I'll have a look at the link & see if that gets me further - thanks for that.

Anyone any other ideas??

[shakeyjake]

mine does this. Idles like an absolute dog when cold for about a minute then smooths out and runs sweet as a nut. The cold start valve is at fault but mine is a kjet, dont know if the digi has one of those

[KingNine]

Yes, the digi doesn't have a cold-start valve & fifth injector as the Kjets do (my Mk1 did). I'm told it is all done with ref to sensors.

[rubjonny]

blue sensor is the only thing that handles cold starting (and warm running too)  if you put a gen VW one in there I'd look elsewhere for the problem.  Maybe your idle switch isnt quite right, check it clicks when the engine is stone cold.  After that I'd be looking for air leaks, then put it into setup mode to see what the base idle is like (the 80 degrees, blue sender off and rev 3 times thing)

[KingNine]

Used a sensor (blue) from GSF, do the 'real' VAG ones make that much of a difference? I'd have thought not but am prepared to be corrected on this. I wasn't aware it was the only thing that handled the cold/warm running - thanks for the tip.
When I get chance next week (working 'til then) I'll do a full setup check. I very much doubt it's an airleak as otherwise it wouldn't run right the rest of the time.

[rubjonny]

apparently they arnt very good, I've only ever bought VAG ones so I can't say from personal experience. I do know a faulty one will make the car either not start or run badly!  They're only about £13 from VAG though if you run out of other ideas!  A couple of drops of machine oil down the fpr can fix a sticky one though I'm not convinced that is the problem.

If you havent swapped the vac lines I'd do that now, they really effect the running of the digi, especially the line to the fpr!

[dadrathers]

Hey King Nine

Found your thread using the Search facility - sorry all to ressurrect it but it is exactly the same problem as I am having at the moment. That is rough running on first start up of the day although not as bad as yours sounds i.e. having to juggle the throttle. All vac hoses have been replaced, blue temp sender was VAG and new about 18 months ago - I am pretty sure it is working OK 'cos when you reconnect it in RJ's tuning guide the timing advances by 30 degrees. New ISV, double checked the idle switch works OK. Retuned and set CO as per RJ tuning guide. (8v PB btw)

Did you find something in the end that fixed it for you?

Cheers