Audi A3 SE 1998 91000miles - Car idles high and cuts out

Are you getting any codes (Dash lights)?
Could be any number of sensors. Hopefully the codes will help narrow down the high idle.

The stalling could be a dirty fuel filter. Has it ever been changed? It also would explain NB 3.

Good luck and let us know. :)

I would try the least expensive options first. Replace the fuel filter, clean the air flow meter, and clean the throttle.

The lambda or O2 sensor has more to do with a fully warmed up engine.

Good luck and let us know.

After rereading your post I did not address the 2,000 rpm idle. That can be caused by a vacuum leak. Check all your vacuum lines for proper connection, brittle cracks, and soft and gummy leaks. Look closely at the PVC valve and the power booster for leaks from their hoses and connections. They require a lot of vacuum. Vacuum leaks can also cause the intermittent stalling.

Changing the fuel filter should be a standard service item done at presribed intervals. Difficult to test for a clogged filter short of removing it and measuring the flow rate thru it. It is cheaper to simply replace.

The O2 or lamda sensors is considered a maintenence item that should be replaced around 100,000 miles. It definitely can be tested. Most better OBDII scanners and the dealer test equipment will be able to monitor it's function and determine it's status. The lamda has to reach at least 600F degrees to function properly. This should only takes minutes.

The air flow meter can be tested but the results are normally a "pass or fail". Testing would not indicate if a cleaning would help.

Their is a throttle position sensor on the throttle body that can be tested. Again it is a "pass or fail". The test will not determine if a cleaning will help. Some throttle bodies come with a special coating to prevent buildup. The manufacturer recommends that they not be cleaned. Check your service manual or the manufacturer to be sure. Cleaning would remove the coating and necessitate more cleanings.

A hookup to a computer will monitor the functions of all engine controll devices and be able to pinpoint any that are not operating correctly. There are several not even mentioned that can cause the symptoms you have described. If you find no vacuum leaks and the fuel filter replacement and cleanings don't help then I would have the computer diagnostic done.

Sorry for the long post but hope this helps. :) Let us know.

My bad. :Oops:
PCV = positive crankcase ventilation. It uses engine vacuum to perform it's function.

Power booster = brake booster It is a large metal canister that has the brake master cylinder attached to it. It's function is to require less foot pressure on the brake pedal to stop the car. It also uses vacuum to perform it's function.

A vacuum leak is air entering the engine that is not metered. It will normally cause a high idle. It will also confuse the computer as to the proper amount of fuel to add for the engine to run properly.

Good l;uck. : Where are you located?

Know a good garage in Burnham-On-Sea. Dereck is a very knowledgeable technician. Might be a bit far for you tho.

The reference to "siphons fuel" is meant for engines without fuel injection and with carburetors.

8)