Hey everyone. My 2000 S4 has gotten a bit testy with me lately. Torque converter went out, engine mounts leaking, O2 sensors went out, you know that sort of stuff. Well for the past few months my engine seems to idle high. Sometimes when I am at a complete stop, my engine sounds like its racing. My RPMs dont go higher than normal, but the engine is very loud and it was never like that before. As soon as I take my foot off the brake, it goes normally quiet again. It only happens when I am at a complete stop. VAGCOM comes up with no codes. Any suggestions would be appreciated.

 

bump for help

 

It only makes noise when your hitting the brakes? I would be looking at the brake booster, or vaccum line to the brake booster.

 

Its the engine that's racing though. The RPMs seem normal, but the engine just sounds loud like it is working hard when I'm at a complete stop. Then I let off the brake and it goes quiet...

 

I think auditech79 might be right, because your brake booster actually uses engine vacuum and thus a leak or similar problem could def. cause issues. You might actually be hearing a vacuum leak, might sound like a "hiss", and could possibly be your extra noise. Also, there might be something going on with the new torque converter (or it's install) perhaps.

You can test your brake booster by lightly pumping the brake pedal until it becomes stiff at the top of it's throw (with car turned off). If it doesn't become stiff your brake booster may be bad. If it works fine, then place your foot lightly on the brake pedal and start the car - if the booster is working, the pedal should "sink" some.

Good luck.

 

I pushed on the brake before i started the car, and it does become stiff. I also pushed it in, started it, and it did sink. Thanks for the advice, at least I hope this knocked one possiblity out that could be wrong.

I was thinking about running some BG 44K through my fuel system and seeing if that improves anything.

The next time I get my oil changed I will also plugs changed, forgot the last time I did that.

Anymore ideas anyone? Thanks for the help so far.

 

Maybe when you get your plugs/oil change done have the shop do a boost leak test, maybe peek at the diverter valves and/or just around in general to see if anything looks strange.

Perhaps see if you can find other symptoms...?

Good luck.

 

Just bought a 2001 S6, all good except she idles v high all the time, nothing to do with being on the brakes, about 1050 rpm! No fault codes! Anyone else have a similar problem?
Love the forum, been v v useful with my old a4 2.8..