When I start my car after it's been sitting for a while (morning or after work) it makes a high pitched grinding sound from the left side of the engine for about a minute, after that it stops. It runs and drives fine. If I rev the motor while it's making this sound, the tone does not change at all, it stays constant.

Any ideas what this may be?

 

umm... not being there it is really hard to say... try to pinpoint to a more exact location, maybe it is the condenser orelectric fan or something that spools on startup.

 

I'm wondering what things spool on startup. Auxiliary pump, fan, etc?? I don't know. I was thinking oh shoot turbo failure but it goes away after about a minute and doesn't change when I rev the engine which the turbo would spool so I doubt it's turbo related.

I can try and take a video of it in the morning and post it when I get home so you guys can hear it.

 

I still have no idea what is causing this. I usually let the car warm up for about 2-3 minutes before I pull out of the garage but I can definately hear some noise that is not normal.

 

The culprit is the secondary air injection pump. It runs when the car is cold started to help with emissions. No one I know tests emissions cold they all want the car at operating temp. I'm trying to figure if I can disable this thing without setting a check engine light.

Only tips have this pump, manuals do not. It only runs for a minute when the car is cold. I can unplug it but I just don't want the check engine light on or my wife will flip out and think the car will need some $1500 repair. The part I found is almost $600 so I can definately live without it. Maybe I'll put some electric tape over the CEL if I can get the gauges out of the dash.

 

Haha. Those are some pretty extreme measures to take. Why don't you just leave the pump alone...? Has it failed? Mine has a similar sound at startup, but as long as it's going away within a minute, no big deal..?

The air injection pump is just preventing excessive emissions at cold startup (which you pointed out). The secondary air injection pump is there to clean up the incredibly rich (with fuel) exhaust that is present for a few minutes when you start up the completely cold engine. The extra air injection greatly increases the rate at which the catalytic converter heats up, so it reaches optimal operating temperature *much* faster and takes over the exhaust cleaning duties.

It isn't there so pesky emissions testers can't sneak up on your car in your sleep or something..... haha.

 

By the 2002 and 2003 S4 is your problem wellknown...you must go to the dealer for a update for your software.
Here in the Netherlands they did the update by almost every 2002 and 2003 S4, by the later models they used already the new software.

Greets

 

I want it gone because it's embarassing. I drive a nice car, when I start it up people look and think what a piece of ****.

 

I have a 2001 S4 with the same problem and it only has 38K miles. If I don't give it that min or 2 to warm up it makes alot of noise, and it will even back fire when I rev the engine a little.

Mine is still under warrenty and I plan on taking it in to have the tranny looked at anyway.

 

Update software like i'd said before....