Snowcar84

Hey boys, for the last few months, my idle has been a little shaky, usually when I start it up, it revs to 1300 or so (like normal) and will either 1) immediatly drop down to like 200 rpms, almost die but catch itself and stutter and choke its way back above 1k and slowly bounce itself out to a steady idle at about 900. 2) Start up fine and idle at 900 for ten seconds, then start the bouncing process.
Regardless of how it starts, once I drive it, and I do a slow downshift, and the rpms fall by themselves asI am disengaging the clutch, it will fall to 200 rpms or even lower, sometimes dying. What do you guys think? Air leak in the vaccuum system? I have searched pretty vigorously, but nothing is apparent... Am I not getting enough of fuel or air? Is my Idle Valve clogging things up? What can the Audi gods Recommend?

4kqlifer

I can't recall what sensor it was. I beleive it is the sensor (temp) right next to the valve cover. No, it's the one sort of attached to the thermostat housing. There is one on top and one below (sensor). I beleive I replaced the top one. I hope this kinda helps.

AudiSport4000

Its discussed here frequently. There are TWO temp sensors on the front coolant neck. The top one is for the temp gauge, and the bottom one controls the mixture during cold starts. The bottom one may be your problem. Try unplugging it and starting the car. But dont leave it unplugged at all times!

Jretal

I know when the ICV died in my brother's CQ he had really weird idling like that, even when driving the car.

If the temp sensor doesn't work, try cleaning the ICV.

Katman

Ohm out the 'closed throttle' switch for correct operation. (The test is in the Bently Manual)

That's the switch UNDER the throttle body, but it's electrical connection is shared with the full throttle switch up top. Connector is near the Cold start injector.

If the ECU doesn't know that the throttle is 'closed' (Because the closed throttle switch is borked), I'm not sure the ECU will kick in the idle air contrrol circuit, so no 'automatic' idle control.

And as you say, your IAC valve may be clogged up too. But that's not too hard to get off and take a look at..

Take a look to the link to Huw's page for more on that..<ul><li><a href="http://www.humanspeakers.com/audi/isv.htm">Huw's ISV info..</a></li></ul>

AudiSport4000

Before I really wrenched on my car I had a horrible cold start issue, it was that lower temp sensor. Also, when I would drive and clutch in, the revs would drop low then bounce back. Tech replaced the faulty sensor, and the idle dropping never occurred again. I just figured it was because of the sensor.

Snowcar84

Just tried upplugging the temp sensor (Lower) and when I started it it ran even worse... so I dont think that bad boy is the problem... When I get some enough time I will clean out my ICV (so it can dry overnight) and hopefully that will help! Thanks