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contrldsub
04-16-2013, 04:47 PM
is it possible for the cam chain to "jump time"?

AWM motor, 140k miles. tiptronic.

walky_talky20
04-16-2013, 04:49 PM
I've only seen it happen when the "feet" actually break and fall off. Otherwise I don't think there is enough slack for it to jump.

zandrew
04-16-2013, 05:12 PM
Can you actually adjust the cam chain tension? Mine is a lil noisy.

walky_talky20
04-16-2013, 06:19 PM
No it is based on the internal spring and the oil pressure. They tend to get noisy when oil pressure falls much below 20psi. So that is something to check. They also tend to wear out and get noisy too. Especially the VVT version.

034Motorsport
04-16-2013, 06:34 PM
is it possible for the cam chain to "jump time"?

AWM motor, 140k miles. tiptronic.

Nope. Even when they lose pressure, there is enough spring tension.

But like Walky said, they can definitely wear out, causing misfires, etc. Or if the guides completely break apart, maybe?

Cgoon009
04-17-2013, 07:29 AM
But like Walky said, they can definitely wear out, causing misfires, etc. Or if the guides completely break apart, maybe?

This just happened to me with a 3.2 a6. The cam tensioner on the driver's side exploded, literally. As a result all twelve valves on the driver's side were bent. The whole engine had to come out, and be rebuilt. Thank god for the guys at RAI, because that sort of work is above my pay grade. If I were you, I would check that out ASAP. The valves could have been saved, had I seen it sooner. Now that's on a chain driven a6, but caution never hurt anyone.

Couple shots of the engine out.

https://cleanaudidotcom.files.wordpress.com/2013/03/photo.jpg

https://cleanaudidotcom.files.wordpress.com/2013/03/photo2.jpg

contrldsub
04-17-2013, 09:48 AM
No it is based on the internal spring and the oil pressure. They tend to get noisy when oil pressure falls much below 20psi. So that is something to check. They also tend to wear out and get noisy too. Especially the VVT version.

this car was purchased for 750$ with the explanation that it was taken to a shop cause of the "ratcheting" noise in the valve train. it was driven home and shut off and wouldnt start back up. we are unable to rotate the engine in either direction past TDC on any cylinder. we pulled the timeing belt and tried opening different sets of valves and rotating the engine to see if there was any change. no matter what set of valves are open the engine will not rotate past the valves. so were taking the head off to check the valves. doing all the timing stuff, and valves if needed before putting it back together.

how far up should the cam chain tensioner move when turning the cam shaft pulley? this one moves upward about 2 inches. that seems excessive to me.

walky_talky20
04-17-2013, 10:45 AM
The tensioners move a lot. This is normal:
https://www.youtube.com/watch?v=-f9NsO_GsVQ

Had a t-belt failure on a 2.7T that came to the shop. Couldn't even get the engine to turn enough to get at the torque converter bolts. Had to pull the heads to do it. Several valves had dropped and were all munched up in the cylinders, jamming the works.

contrldsub
04-19-2013, 04:06 PM
yeah thats about how much it moves. but we got the head off, found a broken valve and lots of bent ones. a couple nice gouges in the head and in the #4 piston, before we got the head off i checked the cam marks and the intake cam had jumped a tooth.