A6forme

Just bought a 2000 A6 4.2 with 130k miles. I got a great deal but it had check engine light on. I brought my laptop with me and read codes before buying car. Codes were for misfire of some cylinders. I cleared the light but it came back. In the morning or when off for more than 20 minutes the engine is rough for the first 15-20 seconds. Otherwise it's smooth with no shaking at all. I noticed that one of the vacum valves on top of the engine in the front has a broken arm. Could this be causing the misfires? What is the purpose of the two valves in the front?
Thanks!

A6forme

Other people having same problem:

http://tech.bentleypublishers.com/thread.jspa?threadID=19055&tstart=0

Anyone know the solution?

Limey Dude

My air valves (or whatever they are called) are broken also, and this doesn't seem to effect the performance of my car at all. My car has done 92K miles now. There is a repair kit availible from Audi for these valves but I'm not sure of the part number at present (will look later.)
I have 2 of them but some older 4.2 engines have just the one.
You could start fault finding be moving your coil packs around to see if the problem moves from piston to piston. That would then tell you if it is the coil pack and associated electronics or the plug itself. It's a start....<ul><li><a href="https://forums.audiworld.com/a6/msgs/616231.phtml">https://forums.audiworld.com/a6/msgs/616231.phtml</a</li></ul>

nemomd

I had a broken arm on mine also. Noticed it after I had rough start up for about 5-10 seconds when cold. My car is a 2001 CPO. The dealer just replaced mine after waiting 3 weeks for the part. I tried to purchase the arm only but my dealer insist that it's not available. This part is a manifold diaphram which is responsible for switching some valves on the intake manifold.My engine has 2. Try to get it used, new they cost over $300 each.
I don't think that this is the reason for your check engine light since mine never lit up. good luck

Limey Dude

I am unsure at present what the repair kit comprises of but the part number is 077-198-327-A. The UK price including tax is 131-GBP
(Approx 247-USD).
I also have a price for the plastic pipes attaching to these valves and the relevant solenoids part number 077-133-331-B (now D not B) these are prone to failure and cracking. The UK price including tax is 29.22-GBP (approx 55.08-USD)
I will possibly seek Audi advice or order the repair kit to see what it comprsies of.
Trust this helps the forum?

MP4.2+6.0

The vacuum devices control the manifold cut over from long runners to short runners at higher RPM. In my car as it does this at about 4000 RPM you smile as you feel the kick in the pants as these things do their stuff--like the secondaries kicking in in a big ole' carb. I expect it will still work without them, but you won't have the same upper end performance.

brittcrowell

<ul><li><a href="http://www.brittcrowell.com/2006/2006-02-08_Working_on_the_A8/imagepages/image35.html">http://www.brittcrowell.com/2006/2006-02-08_Working_on_the_A8/imagepages/image35.html</a</li></ul>