Car is a 1981 240D with 75k miles. Pretty much pristine, though needs a wash and vacuum. Had it out this weekend, and it starts and drives beautifully in the cold (the videos below are taken right after a 25F cold start), but the idle shake behavior Im showing is consistent at any temperature.

Car runs great, starts perfect, zero complaints about power or drivability, but the shake at idle, especially in drive with AC on, is pretty bad. Unlike any idle Ive ever had in my w123 300D turbo cars.

Maybe it just is supposed to be like a tractor, but you decide.

Here's the thing... I can smooth it out with enough idle speed increase or foot on the throttle... But I feel that I shouldn't need to do this. To get it smooth, you must take idle up enough (no tach) so that the oil pressure gauge tacks at the 3 bar point. That's a fast idle compared to the hot idle oil pressure Ive seen on my 300D cars. After you hit that point, it is silky smooth. Cruising or driving even at low speeds is perfect and smooth. Is this just a case of engine mounts, or should I be looking at something else?

Ill probably send the injectors to be popped and balanced just as a why not action... But any other thoughts?

Thanks!

https://youtu.be/6xbaCXZdKtc

https://youtu.be/p26KuAJ3V-U

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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)

On the second video, the power steering reservoir looks a little bouncy. Based on your description, it sounds like you are looking at the right possible causes ... either injectors or motor mounts.

Have you physically inspected the motor mounts? When were they last replaced? Get a really strong flashlight on them from the top and look to see if they are cracked and if one side (or both) appears to be collapsed. Try turning the engine off and then pushing it from side to side and see if you can recreate the rocking on the video.

I would say the chances are better that it is motor mounts as the engine delivers a lot of vibration. Motor mounts need to be changed every 30-50K miles and on your car unless you have service records, they could be original. Injectors on the other hand can clog, but often there will be other symptoms. I'm still on my original injectors @ 145K and am planning to rebuild them in a few weeks just to check the item off my list, not because of any problems.

Another possibility is that something is loose... alternator, ac compressor, power steering gearbox, etc. Check all of these for play with the engine off.

Dkr.

I've been chasing a mild engine / cabin vibration for two years. I had inexpensive aftermarket motor mounts put on and there was this vibration that got worse and worse...not a cylinder miss type...seat vibration, and worse while warming up. I figured well it must be motor or exhaust related. i.e. injection pump, injectors, timing, and on.

Then two weeks or so ago and after much reading, I replaced the aftermarkets mounts (now flat) with OEM i.e. Lemforder / phoenix and all was smooth....butter in the cabin. I've concluded there is a difference in materials used by manufacturers or resellers and that the oem's made all the difference.

Just go for the phoenix, Lemforder, MB brand or don't bother at all (lol)

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1986 300SDL 440,xxx

I was experiencing a bad vibration only at idle and recently replaced the mounts with Lemfoerder and engine shock mounts with genuine Mercedes parts. Much better, but there was still a bit too much vibration (probably why the old mounts wore out rather quickly). I then tightened the rack damper bolt and that made a big difference.

Have to say that I expected much worse from your writeup, before I looked at the video. That's not bad by tractor standards /

Immediate questions:

1. Valves adjusted?
2. Injectors (which you are doing)?**
3. Air leaks? (Primer pump?)
4. Bad tank of 'winter' fuel?

**: I heard what sounded to me like injector nailing when you started it up, a loud tapping sound. I would try cracking the lines, one by one, with the car running to isolate it (or listen first with a stethoscope or long screwdriver held to your ear to isolate which injector is making the sound).

Motor mounts would be a distant last on my list, but based on stuff I have read, it would be possible.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Is this cold or does it improve when the engine heats up? I noticed your mentioned idle speed and increasing it smooths it out. Is this by depressing the pedal or using the idle adjusting knob? I'd also see if the glow plugs are operating if this happens when cold. Also, what type of oil, ie weight. I run 10W-30 Rotella when it gets to Fall temps or early spring temps. Yes, it is diesel rated, see their website. If running a synthetic, never mind.

Does your IP have an externally adjustable have a rack damper?

Sixto
83 300SD

Only the turbodiesels have rack damper bolts. He has a 240d.

I used to have this problem with my '79 300CD. New injectors, valve adjustment, motor mounts and shocks, all the usual stuff. The only thing that made it happy was when one of the local service stations started selling 50 cetane fuel. My feeling is that it was caused by worn valve seats or maybe deposits on the pistons. I would have pulled the head eventually, but the car is no longer with us.