Hi all. This isn't the typical high idle, 1700rpm in neutral situation which most people seem to get and is usually caused by the OVP or idle control valve.

The car is idling at about 1100rpm in neutral and 750 or so in gear. From all that I have read here after searching this is likely to be either the idle control valve or the idle control unit.

What can I do to isolate this further? Both parts are reasonably expensive so I don't want to just through parts at it without trying to be a little surer that it's one or the other or both.

Cheers
Matt.

"...Seems like the idle control valve should be checked out..."


just guessing...

Thanks, I think, any suggestions on how to check it out?

Cheers
Matt.

Seems like the Aussie versions had an adjustment wheel on the bottom...

I am under the impression North American versions had more of a "tamper" proof design...

Could be wrong though...

Best off doing a search on:

idle control valve

Matt, try unplugging the ICV. As I understand, if you unplug and the idle does not change then the valve is not functioning (idle should jump way up when unplugged).

__________________
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.

Thanks Mike, would that completely eliminate the valve though? Is it possible for it to be operating partially?

Cheers
Matt.

Matt,

My take on it is if you disconnect the ICV and idle doesn't increase to nearly 2K rpms, you have a problem with the ICV. Or if it increases but returns to the prior idle slowly, you have a problem.

No idea on how to check the control unit. Someone posted a decent "how-to" on ICV disassembly and cleaning. Might be worth a try at the very least.

EDIT: Just though of this as I hit the submit...double check every connection for possibly vacuum leaks, they could cause a slightly high idle.

__________________
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.

Disconnected the ICV tonight and the revs increased to 1700rpm as expected.

Reconnected and the revs dropped to 1100 or a touch less.

Have already checked all the air hoses, most are new.

Searching here for idle control module or unit only returns a couple of people who talk about resoldering some joints but little detail on exactly what's involved.

How do you check the output of the ICV to see if what it is outputting at idle is correct?

Cheers
Matt.

I would check the idle contact on the throttle switch.

Any info on where that's located and what/how to check?

Cheers
Matt.