Belt Vibration Problems......

[Rx3]

I've noticed my car having strange vibrations at low RPM between idle and about 2000,and the timing being pulled when driving between 1000 and 2000 RPM. After checking my tensioner on the altenator, it didn't help. Today I pulled off the timing belt covers, and for some reason my timing belt is.... twanging. I'm not sure how to explain it, but think of plucking a bass guitar string and watching string vibrate. That's what it looks like my timing belt is doing. If you look at the engine so that the cam gears are facing you, the "twanging" effect is happening after the belt rolls off the left cam to go back down to the crank pully.

Any ideas to what would cause this? The timing belt was changed this summer when I removed my balance shafts, along with brand new tensioners, and I torqued everything according to the factory manual. My timing covers were cracked so I'm wondering if it's just that or something else. I plan on taking out the left front wheel well tomorrow to get a better look. Any suggestions on what to check for?

 

[mitsutuner]

Is your timing belt damaged in any way?
Since your timing covers are off, take a look & see how far the plunger is extended from the hydraulic tensioner--they may not have set it correctly when they installed the new belt or they may have forgotten to tighten the tensioner mounting bolts or they may have re-used your old rusty tensioner even though they charged you for a new one,(by mistake of course) Next check your idler & tensioner pulley bearings, look for rust & grease leakage & see if you can wiggle the outer race of the bearing relative to it's inner race that's bolted to the motor,especially if there's a chance they didn't put new ones on. Take a close look at your crank pulley to see if it looks like it's still in 1 piece.
Be sure to check your ignition timing.
There is probably something I'm forgetting, but if EVERTHING looks & checks OK, it just might be that strange vibration is what happens when you remove the balance shafts, which I hope is not the case because I was planning on doing that to my car at next timing belt change.

 

[Rx3]

Just to update (and for future search engine references), it was indeed the hydraulic auto tensioner. It basically shit the bed, oil from the piston was on the inside of the timing belt covers, and you could push the piston down easily with your finger. I installed a new tensioner, re-tensioned the belt/ adjusted the pulley, everything is cool. Thanks for the help guys.

 

[mitsutuner]

Dude, you are so lucky to find that before you crashed your valves!
You should pat yourself on the back for having a keen sense of awareness of your motor & for pulling the lower timing cover off
BTW, don't know why all the DSMers are so silent, but I was the only 1 that responded to your problem and even though I live in California, I'm the only 1 guy that lives at my house.