Hey Guys,
The car ran perfect before I decided to change out the Aux water pump on my 01 2.7t A6. I beleive I have checked over everything and cant find anything I forgot to put back. The car now runs terrible and is throwing a P0300 code. Any help would be great!!!

Its a random multiple miss-fire fault code. It probably has nothing to do with the aux pump you just changed. Un-less you didn't torque down the intake manifold correctly you probably have a bad power output stage (ignition control module) or bad spark plugs. I would also double check to see if you pinched any wires going to the ignition coils, or if you didn't plug them all the way in.

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00 A4 1.8T

01 S4 SOLD!!!

Thats the thing, I didnt touch any of the ignition components and thought it would be awfully weird for an ignition component to just happen to go out right at that moment.

S*** happens. I would double check you didn't pinch the intake manifold gasket or forgot to plug a major hose in. If it all checks out, eventually you'll get a dead miss fire fault code on one cylinder and it should help you diagnose it for the bad ignition part. Most likely a bad ICM.

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00 A4 1.8T

01 S4 SOLD!!!

Yea no doubt S*** happens, it just absolutely amazes me that I can pull it in the garage running 100% except for a little collant leak and button everything up go t pull it out and now it runs terrible... I had to of missed something however you may be right. Is there any way of testing those ICM's?

You can't really test the ICM with available tools. You would need a pin out box with an LED lead that you would install on the wiring harness from the ECM.
However keep an eye on the fault codes, if it throws a dead miss-fire on like cylinder two perhaps, then you can swap the two ICM's from bank to bank and see if the miss-fire moved to a different cylinder. Both ICM's are sitting on the air box on a 2.7T. They should have a connector on both sides.

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00 A4 1.8T

01 S4 SOLD!!!

Could this thing have anything to do with the problem? I did some more looking around and noticed this was cracked, when I removed it the nipple fully broke off.....

[IMG]local://upfiles/47422/BD36AA4A000D4262874A0BD74711DFEB.jpg[/IMG]

Yes it will have something to do with your problem because it is now dragging air into the system. bypass this if you can or replace/repair the item.

Yep, thats the culprit

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00 A4 1.8T

01 S4 SOLD!!!

Im still kinda conserned...... I didnt think that small of a vacuum leak would cause that much havoc. Does anyone know the function of that little vacuum fitting?