Replaced the motor mounts on my daughter's 84SD and the air filter bracket with about 6k miles on it was broken at back and right end. Installed a new one and decided to take a close look to see why it failed so rapidly. While the engine itself was almost perfectly still, at idle the bracket was vibrating so fast the right end was just a blur. If I increased the rpm by 25-50 the vibration went away completely. It was/is some weird harmonics between the engine and bracket. I decided to try to stop the vibration by increasing the idle rpm's. I loosened the lock nut on the idle bolt and started turning it with a screwdriver but before the idle actually increased the harmonics went away and the bracket became still. Not sure how long this will last but if you have a broken air filter bracket, don't put it down to a shaky engine. Take a look to see if you are getting the weird harmonics and try to get rid of them. I don't see how the new bracket could have lasted more than a few weeks at the rate it was vibrating. (and all the bolts were completely tight).

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Are you speaking of the normal Idle adjustment which is on the engine side of the Fuel Injection Pump or the Rack Damperner/Governor Idle Pin/Bolt?

If it is the Rack Damperner/Governor Idle Pin/Bolt then it is working and adjusted the way it is supposed to be. Which is it removes the shaking without effecting the idle speed. But usually for it to work correctly the normal idle speed adjustment has to be within specs of the normal rpm range listed on your emission sticker. I believe some owners turn the idle speed down to save fuel but it sometimes effects the shaking badly.

There is also various methods like putting a 6 inch or longer piece of heater hose between the intake manifold and the Air Filter Housing as well as different rubber buffers.

.

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84 300D, 82 Volvo 244Gl Diesel

Normal idle adjustment bolt/screw.

Just to be clear, the engine is not shaking, it's only the bracket.

To clarify: The engine must be vibrating to cause the mount to vibrate but the engine vibration is not visible. It's only the vibration on the air filter mount that is visible.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

how do you get to the idle adjust?

I looked at pics of the IP and it looks like the adjustment screw is behind the back plate?

Is that correct, or am I mistaken?

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1983 300CD Turbodiesel

No, it's just a stop for the linkage on the inside of the IP. It's a long bolt/screw with a slotted top for a screwdriver and a locknut where it passes thru the ear on the IP.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

aha,
got it.
I have lots of shake in the air filter also.

engine is smooth, new mounts

I might play around with this if the rack damper doesn't give results.

thanks for posting

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1983 300CD Turbodiesel

The harmonics are very weird. In the process of working on the idle screw I discovered that if I pushed to the left on the last piece of accelerator linkage the vibration would go away.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

so it might be an issue of slack?

you mentioned that adjusting the screw didn't change the idle, but maybe took some slack out of the linkage assemblies?

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1983 300CD Turbodiesel

Perhaps but it makes no sense. Why would slack in the throttle linkage cause such rapid vibration on the other side of the engine? It vibrated like a string on a guitar.
The air cleaner itself was not shaking that fast and I think the reason I saw the problem this time is that the bracket/mount I got from ******** was silver and not black so it was readily visible.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13