Erratic cold start behaviour

[newsh]

A few times recently the engine has had a slightly erratic idle when cold, either revving up or hunting for all the wold as if you're tapping your foot on the pedal at 60 BPM..
Today though after the frosty night it started instantly but went straight up to 2000 RPM as if the throttle was jammed down ( I was reaching for the key in case it kept on going ) blipping made little difference but as it warmed it gradually settled down. Also last night, when fairly warmed up, it died approaching a T juction, something its never done before.


Any ideas chaps?

[Greg_S]

Lamda probe or ISV maybe? or could it be the temp sensor in inlet manifold?

Im probably barking up the wrong tree but worth a try.

Greg

[newsh]

Temp sensor maybe, yes, I'll see if Pete has a spare we can try.

[s2avant]

Mine did the same sorts of thing when my ISV was playing up.

Random idle speed (800-2000rpm) and cutting out at junctions. The most embarrasing thing was pulling up to trafiic lights and having the idle bounce up and down. Everybody thought I was trying to race them

The cylinder in my ISV was scored from where the previous bodger, sorry owner had tried to clean it. I can only assume he had tried to clean it with sandpaper or a screwdriver rather than the more traditional carb cleaner.

Ben

[newsh]

That sounds pretty much like it, so is that the ticket then? Just wash it out with carb cleaner? Or WD40?

[APNess]

This is *exactly* what happened to mine the other week. Cleaned ISV out twice cured prob. Also put 10k boost in - throttle response does seem sharper now, must admit. Get some brake/carb cleaner from halfords, take ISV off, spray inside, wait for crud to come out, keep spraying till clear stuff comes out, refit, and presumably repeat every 20-30k for trouble free life.

PJ

[newsh]

This is *exactly* what happened to mine the other week. Cleaned ISV out twice cured prob. Also put 10k boost in - throttle response does seem sharper now, must admit. Get some brake/carb cleaner from halfords, take ISV off, spray inside, wait for crud to come out, keep spraying till clear stuff comes out, refit, and presumably repeat every 20-30k for trouble free life.

PJ

Thank you dear boy, I shall do as you suggest

[Greg_S]

ive been having a similar problem on mine recently so will have to give the ISV another clean. Hopefully it isnt anything else more expensive

[Greg_S]

Gave the ISV a clean today and the problem seems to be solved now can VAGCOM actuate the ISV so it moves?

[Corey]

Gave the ISV a clean today and the problem seems to be solved now can VAGCOM actuate the ISV so it moves?

No but the output tests can.

[Greg_S]

Will be handy to give that a try and see what the movement is like and clean it at the same time. i dont have VAGCOM so will have to wait til another time.

[Greg_S]

Its started to do it again, the revs seem more stable but when you goto change gear or come to a stop the revs drop and the car sometimes stalls.

Any idea what the cause is & the solution?

[QuattroFever]

mine has started doing this too, mostly on startup but sometimes after a long drive too!

Very strange, some times its good as gold and then sometime it plays up?

The idle has always been a little erratic but not this bad! nearly stalls now!

Do you get thick smoke while the revs are bouncing, more so when they drop low like 300rpm?
I've only noticed smoke at start up but it's only been dong it for 3 days now and i only noticed the smoke today when i went to put something in the boot.

I have recently fitted a cone filter and it has no heat shield? Have you?

[iain1067]

My idle drops a bit and comes back up when the car is warming up but after that it's fine, had the same thing on my Urs4 too, having changed the O2 sensor recently i found that the idle was better during warm up.