For a day or so the '83 motor that I swapped in to my '77 worked pretty well, but suddenly it has developed this habit of bouncing the entire car up and down at idle. I caught people laughing at stop lights twice today.

Mounts are all new. Power on take-off is down a bit, but once the turbo starts to spool everything works just like it did. Idle seems fine. Prefilter is clean. Any ideas?

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- K.C.Adams

'77 300D Euro Delivery
OM617 turbo / 4-speed swap
404 Milanbraun Metallic / 134 Dattel MB-Tex

Current status:
* Undergoing body work

My '77 300D progress thread

I had a similar problem like that once. My 81’ NA 300D was violently shaking to the point it a) sounded like it was going to blow up at high RPM’s and b) was impossible to have a conversation inside the cabin.

We had the mounts replaced by an indy and it was worse!!! We were flabbergasted. So we took it back and they replaced them again with the highest quality mounts avail. Car is smooth as glass now.

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1982 300TDT
1991 190D
2022 Metris

I have a sharp pain in my wallet, now. Will keep your experience in mind!

__________________
- K.C.Adams

'77 300D Euro Delivery
OM617 turbo / 4-speed swap
404 Milanbraun Metallic / 134 Dattel MB-Tex

Current status:
* Undergoing body work

My '77 300D progress thread

It sounds like a cylinder is dropping at idle. Possibly a piece of debris has partially plugged an injector.

I would do a crack test on all the cylinders and then, if you find one that is not effecting the idle quality, remove it and move it to another cylinder to see if the problem follows the injector or if it stays with the same cylinder.

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-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

One of the possibles is an Air Leak.

Does the shaking change with the Engine Temperature?

If you still have the 77 Engine and Fuel Injection Pump try swapping the Overflow/Fuel Pressure Relief Valve.

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84 300D, 82 Volvo 244Gl Diesel

Could you just need a valve adjustment? My 81 300SD would shake like that at stop lights most of the time (surprisingly about one time in 1000 it would be exceptionally smooth - never figured that out). Anyway I had the valves adjusted after 250K miles and it smoothed right out. Pretty smooth at a stoplight now.

A surging idle will make the rear of the car bounce. Does the car bounce in neutral?

Assuming the injectors are OK, I vote for a valve adjustment. Relatively easy and should probably be done anyway. Good cheap starting point.

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1981 300TD 310k miles
1970 280sel 172k miles
1966 230 Fintail 162k miles

"Where are we going? And why am I in this hand basket?"

I did perform a valve adjustment before driving the donor car home. that was something like 90 miles, and it has been started only a handful of times over the past few years, so I would expect it to still be spot on, but I can certainly check it.

yes, the shake is different depending on engine temp. It should also be mentioned that the thermostat has also apparently failed open, but that started after the shake began.

what a shake. it's like the car transforms in to a giant magic fingers bed at stoplights. LOL!

__________________
- K.C.Adams

'77 300D Euro Delivery
OM617 turbo / 4-speed swap
404 Milanbraun Metallic / 134 Dattel MB-Tex

Current status:
* Undergoing body work

My '77 300D progress thread

A couple of ours did that too, ended up doing injector nozzles, rack damper bolt, and valve adjustment....now no shaking at all.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Does your car have a tach? I was going to ask, if you observe the engine "hunting" or "loping" at idle alongside the shake?

How about the cigar hose - did you replace it with a straight fuel hose? What kind of mounts did you get? Some are rated for 240D's, IIRC. The shape may look similar but the durometer may be off. This unit of measurement defines the hardness, I'm not sure what the number should be for turbo diesel vs non turbo diesel. Your '77 should also have the 3rd mount behind the pan, but the turbo engine should not need this.

Did you add the engine shock absorbers and corresponding mounts? IIRC only the turbo had them.

x2

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1983 300SD "Guderian"
1987 MR2
2015 Camry
2015 Chevy Spark
2006 Hyundai Tucson

X3.
Mine shook after the Engine was hot. The Valve Adjustment and rebuilding the Injectors took away most of the shaking.
Motor and Transmission Mounts along with the Rack Damper Screw took away the rest.
I also had a tiny Air leak that when fixed helped.

If I could not live with the shaking (shaking contributes to the loss of Crankshaft Dampers/Pulleys) I would re-check the Valve adjustmen. If for no other reason that when you are trouble shooting something what ever you do not check often turns out to be the cause of the problem.

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84 300D, 82 Volvo 244Gl Diesel

Tach from the donor car is installed, but I have not put permanent power to it. There is an ever so slight amount of idle hunt.

Cigar hose is new... And cigar shaped.

Engine and tranny mounts I will hesitantly acknowledge are uro branded, and ordered locally specifically for the turbo motor. I will say that they seemed not to be an issue for the first two days of driving when the shake was non-existant.

I left the center T-mount off, as the donor car had no provisions for one.

The turbo donor had only one installed engine shock, but the motor mount arms clearly had provisions for two. The '77, oddly enough, has three different shock mount ears installed already, two of which line up perfectly with the turbo motor. Both of my shocks are totally shot, though.

I'll check valve adjustment today at some point.

__________________
- K.C.Adams

'77 300D Euro Delivery
OM617 turbo / 4-speed swap
404 Milanbraun Metallic / 134 Dattel MB-Tex

Current status:
* Undergoing body work

My '77 300D progress thread

This thread needs a video... sounds like an episode of Seinfeld. my Quint is rough at idle but no real chassis vibration.

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85 Merc 300D - Unwinding 31 years of wear
86 VW TD
Mahindra Diesel
Iseki Diesel

In 2007 I didn't own a diesel.