audiophyl

Following replacing the intercooler hose, I ran into the annoying oscillating idle caused by the ISV. I cleaned it using throttle body cleaner, and things cleared up... for a while.

I then ran into a different, much more obnoxious oscillating idle issue which appeared to be tied to the decel valve. Sure enough, pinching the hose off eliminated the issue... I had read a post on this forum indicating I could do without the decel valve, so I have bypassed it for the time being.

Now the car idles at 1800, but will occasionally jump to ~3000. If it has surged to ~3000, it will surge further when shifting, but will return to ~3000. Every now and again the car will drop back to 1800. I know it should be ~750, so I'm very concerned.

I have verified the function of the idle switch via DMM, and taken the time to visually inspect, re-solder, and re-seat it to be 300% confident. I have verified the correct operation of a handful of sensors as per sjmautotechnik.com instructions. The screw on the intake manifold is all the way in, but repositioning it doesn't change things much at all. I have cleaned, re-cleaned, and re-re-cleaned the ISV with no results.

I am stumped. Everyone thinks I want to race when I pull up to a stop light unless I let out the clutch a bit... but I don't want to burn out my clutch!

Any thoughts? I'm going cross-eyed combing through all of Scott's info. It has been an invaluable source, but I'm not able to find anything which affects my current situation.

Thanks in advance!

-Philip Barton

yodasfro

Leaky injector/inj insert seals other vac leaks??? Idle controller........

jurq

If the fuel distributor has been leaned out, the motor will idle at a high rate of speed. Turning down the idle screw will not lower the idle when this is the case. Run the diagnostic test, as per SJM, and check again for vac leaks.

These would be my best guesses.

HTH,
Jim

treehunter

Depending on how you did the bypass you could have a vac leak and as the throttle switch sits on the intake butterfly shaft that might be the cause if it has been rotated too far then screwed down.
As per SJM, you should hear the switch "click" when the throttle moves off it's stop.

Idle valves have rubber seals that wear out, try blowing through either end, if your ears pop, it's good, if it flows she's done.

HTH.

boxerfan

Are your floor mats interferring with the pedal? Sometimes the thicker winter mats can jam the pedal.

audiophyl

I disconnected the decel valve, plugged the hose, and plugged the hole in the igloo(?)

Is there anything else I should have done to bypass it?

Thanks for the info,

-Philip Barton

audiophyl

That happened to me last winter...

It was the first thing I checked when this problem started!

-Philip Barton

treehunter

That should do it. Have you checked those ISV seals?

danfromsyr

on my 875000 TQ I carry a HIGH Idle when the climate control is set to allow the AC to run (ie defrost cycles AC)
my AC is not full, so I don't get the compressor drag on the engine it is expecting which allows for my higher Idle.

I use the ECONO setting and the Idle sits right where it is supposed to..

I intend to repair my AC by this next summer..
Dan in NY

audiophyl

Sure enough, the ISV seal is bad. Thanks for the tip, I've got a new one shipping.

I had noticed a segment in the Bentley which discussed adjusting the duty cycle (and will readily admit I have no idea what this means). The procedure includes removing an aluminum plug from behind the fuel distributor, and it is painfully obvious that has been done on my Audi.

Just for a test I stuck a long screwdriver down there and gave it a light push. Sure enough, my idle dropped down to something reasonable. I made the adjustment, and now I'm around ~1200. Any lower and the car dies.

I'm guessing this isn't the optimal solution, as there is no way for me to know the mixture is correct... Correct?

Thanks again!

-Philip