bkv

Normal idle is about 1000 rpm, a little high but..
When I turn a/c on, idle drops to about 800 when the a/c clutch is engaged and the engine is still cold after start. After about 10 min the idle drops to about 400 and the engine stalls sometimes when a/c clutch is engaged.

Thanks

Spanglear

Might be a problem with your idle stabilization valve. This should compensate when the engine is cold or you are using alot of electrical power (e.g. AC, rear de mist, headlights, fogs etc.) by allowing more air through, bypassing the throttle plate.

Its just like when you have to push more on the throttle to get up a steep hill to prevent stalling - you are opening the throttle plate to let more air through & maintain revs.

Try cleaning it with carb cleaner as they tend to get clogged with sludge.

bkv

It appears to be working
Any other ideas?

Thanks anyway

QCRAZY

...I'm not sure exactly what Audi calls this item!!

When you turn the A/C on this solenoid is supposed to increase the idle speed to compensate for the increased load on your car. It sounds to me like this is not working on your car!!

It would help if you posted the year and model of your car!!

bkv

I was looking for something like idle up solenoid, but did not find one. I have something like that clicking on the top of air intake rubber, connected to coal canister as well. It clicks well. Where else that thing can be?

Thanks

QCRAZY

..what is clicking?? You're talking about item #11 right??

<img src="http://catalog.exist.ru/pic/parts/VAG01579.gif">

Item #11 is the charcoal canister shut-off solenoid. This is not related to engine speed.

I also grabbed out my Bentley manual and checked to see what they list for the *idle-up* valve. From what I could gather from my Bentley manual it (the idle speed increase) is all done at the ISV. The process electronically controlled by the fuel injection computer and the adjustment is eventually made at the ISV. You may want to see if you can get your hands on a spare ISV. I've never had much luck cleaning ISV's myself!!

HTH!!

bkv

Yes, I was talking about item #11. I will try to
replace ISV. I saw it is working on the engine start up (at least the valve is moving inside), but I have no idea what is going on when the engine is hot.

Thanks a lot

Spanglear

Maybe it is malfunctioning slightly. You can do various electrical tests depending on what type it is. Simple test is resistance across terminals. Also duty cycle tests with dwell meter.

bkv

I did test the resistance across terminals (only two are there, it is bosch), but nothing else. I saw it is moving when I turn the starter, but no other tests. How else can I test that d... valve?

Thanks

Spanglear

Forget AC for a minute. With engine idling, if you load the system by turning on several things other than AC, does the idle speed change in the same way? should barely change whatever (maybe dip slightly for an instant)?