rk

I have an 86 951 that I purchased a few months back. Yesterday as I was leaving work there was a load knocking noise coming from the engine. It was knocking about once every second sitting idle. Against my better judgement I drove it home. The knocking went away, but it was replaced by an engine vibration. I don't notice the vibration at idle, but once the rpm reaches about 2000 a vibration "pulse" starts. About once a second the I can feel the vibration throughout the car. The higher the rpm the faster the "pulse". The vibrations occur whether I'm moving or sitting in neutral. Any ideas?

ae1969

I would think a motor mount.....has gone ...Kappputttz.....

Renntag

Yeah, I would tend to agree. That is very common.

Good luck with it. Let us know what you find.

rk

I finally finished replacing the motor mounts this weekend and it seems to have worked. The pulsing vibration is gone. I still seem to be getting too much vibration at higher RPM (~4k), but I think I just need to tune it up (new plugs, air filter, etc.). The old motor mounts didn't look to bad, but I think the passenger side one was leaking a bit.

Thanks ae1969 and Renntag951.

Rob

What kind of shape is your Balance shaft belt in? could the belt have been making the noise?

Later,
Rob

Greg Hammond

If your balance shaft belt has broken, you have a very dangerous situation at hand. You need to pull the belt cover(s) off and inspect the condition of your belt ASAP.

It's possible the belt skipped a tooth due to being too slack, and that's just about as bad. The balance shafts typically counter any vibration in the engine that would otherwise be absorbed by the engine mounts. New mounts usually takes care of MOST vibration issues.

Greg

rk

Correct me if I'm wrong, but I thought that if the balance shaft belt was off you would notice it most at idle. Idle seems fine, it just at the higher RPM that seems to vibrate. I wouldn't say its a bad vibrartion, its not shaking the the car but I do feel it through the stick.

Another possiblity is that I got some bad gas. It was not long after I filled up that I started noticing the problem. I'm sure I got the 92 octane gas, but I'm not sure what the quality of Diamond Shamrock gas is.

I am due to replace the cam shaft and blance shaft belts so that will be the next job. I haven't decided if I'm going to do it myself or have a shop do it. The shop said it be about 450 to replace the belts, tensioners, and idlers. That price didn't include new seals/gaskets which I know I need because I'm leaking oil.

Thanks for the info.