Hi all, great forum here!

Ive been searching almost nonstop since I got the car yesterday, and I cant find anything specific really to what Im feeling.

Most problems others are having seems to be related to a bad clutch or something like that.

Anyways I have a 94 auto, has 171k on the clock, has been well maintained etc. HOWEVER above 2500-4500 there is a very bad vibration that I can feel through the whole car. I thought it was u-joints, but it does this in neutral/park. I pulled power to the injectors while the car was running and all of them appear to be working. I also get good gas mileage.

It was hesitating a bit, and missing slightly on maybe one cylinder. All the spark plugs and wires appear to be new. I doubt the optispark has been replaced. So Im assuming that could be bad.

Heres my problem, Ive never had a car vibrate so badly, so Im unsure which could thing be causing this problem. I dont believe throwing money at the problem would be helpful. I havnt ruled out the balancer, I dont know if it would cause anything this severe though?

So should I just replace the optispark on principal since its more than likely original? Or do the proper testing with a timing light?

I dont think I have a leaky head either, I dont get any odd smoke. It does smell rich though.

Any advice would be appreciated. I could look up the specifics if I can get some direction
Also it seems to be low on power, would a miss cause this? I think my 2012 Ext cab Sierra would win in a drag race at this point.

THANKS
Mike

 

What condition are the engine mounts in?

Any codes?

How old is the coil? What condition is it in?

Have you tested the ICM?

 

Ah I have not tested the ICM

I suspect the coil may be original, and no codes.
I'll pull the coil plug on the opti end tomorrow and see what its doing.

I have also ran it at night to see if I could see the plug wires arcing, and no dice.

Will update after I have tested these things. Thanks for the quick reply!

 

UPDATE -
Ive replaced the optispark and it cleared up most of the vibration. I still have a bit from 3800-4000, in neutral or gear.

Im suspecting maybe the exhaust vibrating against something? Or motor mounts? Any input would be appreciated

 

If I had just bought a car, I would run a leak down test to make sure mechanically, the motor is all right. Then I would change new plugs, and wires. If the vibration is still there, at least you will have it narrowed down to none of the above.