2.0 tfsi idle speed.

[blade7]

Changed PCV valve as the idle had crept up to 1200 rpm, seemed to cure it for a while but occasionally it idles high still, except when the aircon is on. what's next ?

[ManOpener]

Vacuum leak elsewhere in the system is a likely culprit. You could see if resetting the throttle body alignment helps- http://wiki.ross-tech.com/wiki/index.php/Throttle_...

[SuperchargedVR6]

What is the part number of the breather you used? If it's 06F129101P, you need the updated rear breather pipe to go with it - 06F103215B. If the two aren't fitted together you can indeed get some idle problems.

If you fitted 06F129101R, that should be OK with the older (check valve-less) rear breather i.e. the metal pipe that joins the turbo intake hose.

[blade7]

Thanks for the suggestions, it was the "R" breather that I fitted. Idle speed was fine today without the AC on ?

[RammyMP]

Mine always seems to be smoother at idle when the AC is on, the revs judder slightly when it's off. st explaination I know!

[charlie7777]

It could be something as basic and simple as a faulty water thermostat. This is still the primary temperature control on engines. Without this working correctly all other sensors and controls may base their actions on ‘false’ inputs. Cold start mechanisms for example may activate thus raising idle speed.

[blade7]

Will that show up on a diagnostic check and what's the typical cost for one ?

[charlie7777]

It may not show on the check, the thermostat is such a low tech item. They engine will just be running too cool at various times. They are usually cheap and simple to replace. The whole job for under £50 . Its a good place to start when having this sort of problem.

[blade7]

Seems to get up to temp on the gauge normally and the cold start idle drops down within a few seconds.

[charlie7777]

Thermostat problems often show after a run on faster road on cool days where the radiator is able to over cool the water through the engine. When stationary and the radiator is not cooling much everything can seem OK.

As I say it is worth checking.

[SuperchargedVR6]

RammyMP said:

Mine always seems to be smoother at idle when the AC is on, the revs judder slightly when it's off. st explaination I know!

The idle speed is raised slightly when the AC is on, so it feels a bit smoother. Mine's a bit lumpy with the AC off as well but it's done 91K and could do with a decoke.

[blade7]

charlie7777 said:

Thermostat problems often show after a run on faster road on cool days where the radiator is able to over cool the water through the engine. When stationary and the radiator is not cooling much everything can seem OK.

As I say it is worth checking.

Thanks .

[blade7]

Still getting occasional raised idle speed, giving the N80 valve a wiggle results in it clicking and the idle drops, time for a new valve and other than Audi where from ?