Engine runs rough and shakes/vibrates. HELP

[Rob4]

My 1989 N/A 6.2 ran great until about 300 miles ago. It gradually started to vibrate slightly at idle. When I barely increased the RPM, or turned on the A/C, I didn't notice it. It has continued to get worse and now runs rough/shakes/vibrates at any RPM.

It starts just fine and does not run hot. It makes no difference if the clutch is in or out. I have removed the serpentine belt but it makes no difference. I just replaced the injectors today but it didn't help. The engine doesn't clank or clatter beyond what a diesel normally does.

What's happening? It seems to start and run great, it just shakes and vibrates. I'm afraid to drive it anymore for fear of tearing up the engine. It's my daily driver and I hope it's not bad news. Thanks in advance guys for any help you can send my way. :confused:

[trbankii]

Others will chime in here, but my first thought is to take a look at the harmonic dampner on the front of the engine...

[john8662]

How bad is the shaking?

If you pop the hood and watch the engine running is the engine rapidly shaking side to side?

Vibrations can be transmitted to the cab and frame with bad engine mounts and or transmission mounts.

But, if the engine is indeed running poorly, then it will shake the truck no matter what really.

Are you getting any smoke during this?

J

[Rob4]

Sorry, I was away from the computer yesterday. I'm still having the shaking/vibration problem. I thought about the harmonic damper as a problem. I had replaced it about a year ago but that doesn't mean it's not bad. I will go out today and put the old one back in to eliminate or confirm the balancer as a problem.
I have checked the motor mounts as well as the transmission mount. If the hood is raised, the hood will shake side to side. As the engine rpm is increased the hood shakes more violently side to side. It seems that the engine and body both shake together. There is no smoke from the engine. The engine has about 150,000 miles.
Can the timing go so far out in 300 miles or so? Also, would the timing even cause this type of problem? What about the IP? I thought that when the pump went bad it would affect all cylinders equally. Any other thoughts? Thanks.

[Rob4]

I found the problem, but now I really have a problem. I removed the crankshaft pulley with the rubber ring in it that drives the serpentine belt . (This is what I replaced about a year ago. Some parts stores call it a harmonic balancer, but not really?). Anyway, after I removed it I put a wrench on the bolt that holds the harmonic balancer to the crank and it was loose. I pulled the harmonic balancer off and the keyway in the balancer was badly wallered. The keyway in the crank is also badly wallered--probably 0.030 wider. It appears that the key broke about halfway down in the crankshaft and the bottom part of the key is stuck in the crank. The top half of the key tore things up. Now what? I hate to think of tearing down the engine. Anybody have any ideas on how to repair this mess without replacing the crank? :(

[Slim shady]

I know I will take heat for this, but here goes. I had a piece of equipment that was expensive and had a drive hub that had done the same thing as your balancer.

I ended up repairing the key way and used Lock Tite shaft repair. There are slip fit repair and there are void filing repair repairs. Very similar to red loctite that we use on studs that never come out without heat.

The biggest part of the job was making sure the hub ran true. I managed to get the hub trued up and use the shaft repair compound (fills voids) the drive hub is still in operation today and regularly takes 60 hp loads driving a HYD pump. Not a perfect solution but if done correctly it will by you time until you can get a new crank and take the time to rebuild it.

I would never have done this if I could have replaced the shaft but the cost was just way to expensive. That being said broke is already broke and this is still working after 2 years, I had nothing to lose.

if you need to remove the crank shaft dampener after it WILL take heat to get the dampener off.