Misfires - Unusual Timing belt tension failure
 

I have a 2002 Allroad, purchased in October 2011. Did the timing belt job in November 2011 when the car had about 100,000 miles on it since I had no service history information. The car now has about 125,000 miles on it, I don't drive a whole lot and have another car that I drive more in the summer.

The weekend before last, i had some noise start from the engine. I wasn't far from home, so i drove home and parked it. Took a quick look for the source of the noise the next day and took another short drive, then barked up the wrong tree with the cam position sensors since that was the only code that i got from the OBD initially. Then trying to diagnose while running in the garage, i got a CEL, pulled codes and found misfires on all cylinders. This pointed me to the timing belt.

Yesterday, I dug in and got to the timing belt. Sure enough, lost tension in the belt. Pulled the dampener out since i had read online about aftermarket damper failures. Was getting ready to order parts tonight, but then thought a little more about it and realized that something wasn't right when i pulled the dampener out, so i went out to the garage to inspect again.

Turns out, the dampener might not have been bad at all. It appears that the pin in the tensioning roller slid through the roller to the point where the lever no longer could push on it. Seems to be a rather strange failure to me, has anyone else seen something like this?


https://cimg4.ibsrv.net/gimg/www.aud...3570acfe6.jpeg


https://cimg5.ibsrv.net/gimg/www.aud...8f0130bfc.jpeg


https://cimg6.ibsrv.net/gimg/www.aud...93772bb20.jpeg


https://cimg7.ibsrv.net/gimg/www.aud...dfc875792.jpeg

So, since the previous post, i replaced:

Timing belt
relay roller
tensioning roller
tensioning lever
damper

When installing, i loosened the cam sprockets and used the lock bar on the camshafts. I did not use the crankshaft lock pin, just went off of the mark on the pulley. Put everything back together last night, started it, it runs rough with a blinking CEL and codes for misfires on cylinders 1,2, and 3.

So, the conclusion that I'm jumping to here is that i have bent valves from the timing belt failure. I realize that not using the crank lock pin leaves some margin for error, but I would expect that if the crank was off, i would have misfires on all cylinders, not just one bank. Can anyone see any other possible explanation?

Well, if anyone is following along here, a friend came by today with a compression tester. Good compression (175 psi) on cylinder 4, nothing on cylinder 2 (0 psi). Ran out of time before checking other cylinders, but the assumption here is 1,2,3 all have bent valves and 4,5,6 are all fine. :(