Engine Vibration 1991 B6D

[Skrapbob]

hmmm! To be clear, the vibration is constant, through all rpm's. It just seems to scream a little louder at 3k an 5k+. I have checked the timing notches more than once. They have always lined up nicely at TDC. Is there a good way to count the teeth of the belt to be sure of cam alignment? I would love for this to be a performance problem rather than a balance problem.

What is the chance of the harmonic balancer/pulley just being old, with a hardened rubber dampner?

[FestYboy]

Have you done a compression of leak down test? A weak cylinder can cause vibration...

[Skrapbob]

Compression is 150,140,140,130

My next plan of action is to check the timing at the cam gears again. I'm getting pretty good at tearing this car down and reassembling! :-)

[WmWatt]

The Haynes manual suggests there should be no more than a 5% variation in comresssion accross all cylinders. Those reading have a 15% variation beween #1 and #4. I don't know if that's enough to cause a problem.

[F3BZ]

i would suspect the flywheel. especially if its some off brand from a far away land. is the flywheel and crank/pistons balanced as a complete assembly when the car is built originally?

[FestYboy]

Flywheel is neutral balanced (or should be).

[WmWatt]

If the front end is raised on stands so the front wheels are off the ground the engine can be started and run in or out of gear while the car is stationary and you can look inside the engine compartment while the car is running and maybe help isolate the problem, or maybe you are already doing that.

[FestYboy]

^ unless it's a load based vibration...

[WmWatt]

^ would that mean more vibration going uphill? Could try that too.

[FestYboy]

Possibly.

[Skrapbob]

I have a few minutes tonight so as time allows I am going to start a tear down to the timing belt. Will post with any updates when possible. Thanks for the suggestions.

[Skrapbob]

Some pics from tonights adventures

[Skrapbob]

[Skrapbob]

[Rick the Quick]

I don't think the 20 psi difference in compression (between highest and lowest) would cause the vibration. My next step would be to make some calls and find a shop that could check the flywheel with pressure plate for balance.