Just wondering if anyone has had a similar problem before? When starting the g from stone cold the idle is shockingly bad, it will stall if you let it. Once driving for about 10 mins and engine is nice and warm its fine... Any ideas?

Clean the ISV with petrol / carb cleaner - it lives under the inlet and is connected to the plastic boost pipe leading to the TB.

If that fails - try blue temp sensors and get your Air Flow Sensor reading checked and adjusted,

If you need to know what to set the resisitance to contact PSD.

Dave

the COpot should be adjusted to 550ohm's or there abouts, IIRC.

How would you go about cleaning your ISV with carb cleaner? just un-screw the jubilee and spray down the pipe? My ISV popped off once...what does it actually do? sorry for butting in...

same problem but new air filter helped a little but this sounds interesting but i dont no what you mean ? or how to do it? cheers jake

I'd try a temp sender first,a dodgy reading will cause poor fueling from cold as well as cleaning the isv.

My blue temp sender(vag) lasted exactly 3 months, changed it at no cost under parts warranty!!!

Thanks for the replys, its had a new aire filter not so long ago when I did a full service. Co Pot was set correctly when I was having some running probs a while ago, how much are the blue temp senders from VAG? Dont know what you mean by ISV, can anyone give anymore info please?

Thanks :)

Thanks for the replys, its had a new aire filter not so long ago when I did a full service. Co Pot was set correctly when I was having some running probs a while ago, how much are the blue temp senders from VAG? Dont know what you mean by ISV, can anyone give anymore info please?

Thanks :)

The plastic boost pipe that runs to the throttle body has a pipe connected to the underneath - which will run to the ISV then from the other side of the ISV it will connect via another pipe to the inlet maniold.

My ISV bolts on using 2 10mm bolts iirc...

It is a valve and needs cleaning using the above - remove it - clean it or replace it and refit.

That should sort you out!

Thanks for that Dave, will give it a bash asap.

It doesnt seem that easy to remove from memory...is there anything more you had to do to remove it??

It doesnt seem that easy to remove from memory...is there anything more you had to do to remove it??

I happened to do mine with the inlet out the way - as I was changing it over for the GT item at the time...

It is doable with the inlet bolted to the head - however isn't "easy" and requires a bit of patience....

lol, just had a quick check and the two 10mm bolts that secure it are missing...

Just took the ISV off and give it a really good blast with some carb cleaner, the idle seems to have improved but it's still not perfect. How would you know if it's knackered?

When I start the car it idles fine for a few minutes then its as if the choke comes off and it runs lumpy, this kind of makes me think there is something wrong with the blue temp sensor, am I going down the right track here?

Oh and to anyone who's thinking of attempting to clean the ISV, its not difficult, took me around 20 mins in total.

Edited 23 July, 200719 yr by Dan-G40

You would be as well to check the blue temp sender, yes. You can generally say that any cold temperature related running issues are down to it giving up the ghost is you're certain you've checked the ISV. A new one from VW was around £13 with an O-ring when I picked one up 2 weeks ago. Give that a try, as for £13 it would still provide future peace of mind even if it didn't need it.

You would be as well to check the blue temp sender, yes. You can generally say that any cold temperature related running issues are down to it giving up the ghost is you're certain you've checked the ISV. A new one from VW was around £13 with an O-ring when I picked one up 2 weeks ago. Give that a try, as for £13 it would still provide future peace of mind even if it didn't need it.

I'll give the stealers a ring tomorrow, like you said for £13 its peace of mind. :)

Right, cleaned the ISV out with loads of carb cleaner, replaced the blue temp sender with a genuine VAG part - same problem! When I start the car it idles fine at about 900-950rpm, then after about 60 seconds it's like the choke or something turns of and it struggles and runs lumpy lower than 900rpm.

Any ideas? this is driving me mad!

Next thing is the Air Flow Sensor in the boost pipe...

It needs to be set correctly...speak to steve @ PSD for the correct settings and you will need a mutimetre to do the job...

Also keep looking for small boost leaks...

Dave are you talking about the co pot/air temp sensor? There is no air flow meter on a mk3 g40.

Dan - is it just that your idle is set too low? As far as I'm aware it should be about 1000rpm fast idle and then drop to about 900 when warm. Sounds like yours might just be dropping too much. there's an idle screw on the back of the throttle body, unscrew it slightly to raise the idle.

The aux air valve you've cleaned out are very annoying things. To be honest the only way to get it perfect again is to buy a brand new one but they're weren't particularly cheap last time I priced one up (although it was a few years ago). Even so, it should only really cause the idle to hunt a bit as the valve is too slow to react to the revs dropping off if you've cleaned it.

Dave are you talking about the co pot/air temp sensor? There is no air flow meter on a mk3 g40.

No sorry - the little sensor that lives in the boost pipe near the throttle body...

When my idle was bad I took it to dubshack and the first thing he did was remove and re-adjust my sensor correctly...

I then replaced my disie and cap and arm and leads and plugs and had the timing done...

Seems to have cured it....

You could be right Hayesey, will set it to 1000 as fast idle and see if that makes any difference. I priced a new aux air valve up at VW yesterday and they want £65+VAT! When you say 'hunt', what exactly do you mean? Excuse the noobishness :)

Dave - If you are talking about the CO pot I've set that to 550ohms, got a guide off Steve at PSD for measuring resistance of sensors etc. Dizzy cap, leads and plugs and timing has all been done a couple of months ago when I was having ignition problems.

well the idea of the air valve is that it opens and closes to allow or restrict the amount of air bypassing the thottle plate into the inlet to maintain a steady idle. When the valve is tired it works too slowly and you get the revs dropping off and then rising again when the valve catches up and opens enough. If it's gummed up with sludge then it's worse and cleaning it frees it up a bit. But as I say the only complete cure is a new un.

I'm having trouble getting my g running smoothly at the moment too but I need to setup the co pot as last night when I measured it, it was reading just over 2Kohms which is 4 times too high.

Set the fast idle to 1000rpm, it doesn't appear to have made much difference. I understand what you mean about the hunting, think the aux air valve may be the problem as it displays these symptoms. There's one on ebay at the moment but its pot luck if it's a gudden or not! Thanks for the help :)

havnt read the whole thread as in a rush, but my car was idling at about 1200rpm and was REALLY hard to drive when cold. Spluttering and stalling. Disconnected the lambda and bam, runs perfectly.

Give that a bash

ay up dan how you getting on????

just wonded as i have exactly the same problem and would be intrested how you solve it.

useful thread guys

thanks dan (I'm also called dan)