weird engine shake
 

what would cause a bad engine shake
all of a sudden at idle now my engine seems to be shaking, rocking more than usual

has brandy new motor mounts within the last two months

1982 300TD 150k on it

Wrong forum... ;)

Check the diesel discussion for rack bolt. Sometimes you can adjust, others you have to replace.p

ph geeze. im a tard.
:)

Double check your motor mounts. That's probably the most common source. I know you've got new ones, but that's the easiest one to check.

Then check

• Rack damper
• Valve adjustment
• Injectors
• Fan clutch
• Fuel quality

What brand mounts did you use? anything besides lemforder or phoenix are crap....also check the trans mount.

engine shocks?

Engine shocks don't really do a whole lot under normal operation. They are primarily designed to dampen engine shake during shutdown.

For example when I put a 617 engine in my 107, I did not include engine shocks. While trying to sort out an idle vibration, I added one. It made absolutely no difference. (The vibration turned out to be engine mounts I had filled with too hard of a urethane formulation to prevent collapsing)

Does the shaking decrease as you increase speed slightly above idle. It could be that at idle it hits a "natural frequency" where the motor rotational inertial and motor mount stiffness would naturally oscillate. If so, hard to overcome with damping, instead better to change the natural frequency. Softer motor mounts would lower it. Why it changed is hard to know.

Does this occur at all engine temps, or just when hot?

If the latter, my guess is the rack damper bolt/pin.

it seems to happen at idle or lower speeds..or when slowing down?
i have a bad feeling one of the motormount bolts came out.
im going to put it up on the ramps in a bit i will report back

thank you for all the answers guys

i ordered a new fuel filter for the tank also.

so my mounts seem fine...thought maybe i lost a bolt or something...they are snug..the chaking seems to be intermittent..i am getting ready to do a vlave adjustment and valve cover gasket replacement...maybe that will help woththe shake...i did not replace the transmission mount...would that cause the shake?

Does this happen when the engine is cold?

Or just when hot?

If it were the valves, I would think that you could hear them tick. Not that you should wait until they tick to adjust them. - do make sure you get the order right. Search for rack dampener adjustment... There is a thread that describes how to adjust it, and even what color bolt to look for (if memory serves correct). Good luck!

Need to refine what you mean by 'shake'.

I am going to say what I use as a guideline for attacking the problem. None of this is written in stone.

If it's a gentle, loping shake from side to side (that probably rocks the car with it), which gets worse when the engine is hot and much worse when you come off a highway run of more than a few minutes, it's most likely the rack damper bolt at the back of the injector pump (faces the oil filter canister). The original style from the factory was silver, however as the cars age they commonly need to have the bolt upgraded to the new, gold-coloured one. This has to be adjusted, sometimes in concert with the idle speed, to smooth out the idle. If you go this route, shop around as they vary hugely in price from various vendors.

If it isn't a lope but a hard shake, I would tend toward an injector issue. When the shake is bad, gently crack open each hard line at the injector inlet and see if you find one where the idle doesn't change.

If the shake is there all the time, then I would be looking for an air leak into the fuel system as well as the injector issue. Check all the fuel line clamps, inspect the fuel hoses (including the little short one between the inlet (clear plastic) filter and the pump. That gets forgotten and can cause all manner of fun. You can also replace the 'cigar' hose on the return line from the spin-on filter with a section of clear hose and see if there are air bubbles (I have never had to do this, but I have seen it recommended on the forum.)