Jersey Joe

This is for extreme techs.

My 90 idles fine, but as you slowly increase the rpm starting at 1000 up through 1800 there is quite a pronounced vibration that can be felt. Just at 2000 and up to 3500 (that's as far as I wanted to go in neutral) it is smooth. Comming back down, it starts again at 1900 and is there until jut off idle. Any ideas???????? I thought is might be mounts, but it's strange how at exactly 2000 it goes away. Someone suggested a bad cap, plug wire or injector trouble.

HELP

Uproar

Hey Jersey:

I might suggest that you check your harmonic balancer. Mine recently failed. This entailed the outer section seperating from the inner section, it appears that the rubber dampner material may breakdown with age. The uneasy vibration you mention was one of the symptoms. Unfortunately for me the outer section got into the timing belt before I could figure out what was going on.

Hope this helps. You also might put your car up on substantial jack stands and utilize the clutch in and out to rule out the torque tube or transmission related vibrations.

Regards,

Ken

Tommy928

Ken,

What is the harmonic balancing? Where is it located? My 87' automatic has the same symtom as Jersey's car. I have ruled out motor mounts or ignition related problems.

Thanks,
Tommy

Uproar

The harmonic balancer is the Big Orange disc that is right behind the lower set of pulleys, it has the timing marks on it.

It simply is there to settle certain frequencies out of the crankshaft. You might try to see if it appears to be loose. Some are damaged during the timing belt change when people get a bit over zealous and try to pry them off.

Regards,

Ken

Jersey Joe

What is the best way to go about checking it? Do I have to take it off?

Uproar

If it has failed like mine did, you may be able to see that it does not look square to the motor or pulley. Best thing to do is jack up the car and look at it from underneath. Mine actually was spinning and slipping in and out. If you get a hold on it and it moves...then it's shot.

You don't say if you have isolated the drive train?

K.

Jersey Joe

I have not but the previous owner had replaced the torque tube and the clutch. How much of a job is the damper to replace? I assume that if I am going in that deep, I might want to continue on and to the timing belt. Although I am ASE certified, most of my experience is dated, and on other than 928's. Can't be that bad to do except for the tensioning tool need. Looks like the balancer involves the external drive belts, balancer center bolt and perhaps a puller?