1981 240d really rough idle - PeachParts Mercedes-Benz Forum

chelsea's dad · #1 11-23-2013, 10:42 PM

car had 160k when we bought it. owner said original motor was run out of oil so they put a used motor in with approx. same mileage. uses a qt of oil every 150 miles or so but gets 30 mpg (stick). on start up it shakes so hard the front bumper and fenders rattle sometimes. gets a little better after warm up but never really smoothes out. i've adjusted the valves twice and makes no difference. anything in particular i should look for? is it possible that using that much oil it sat for a long time and maybe the rings rusted up? could the cam have gone flat?

thanks in advance

jt20 · #2 11-23-2013, 10:51 PM

Its typical for these engines to burn oil much faster on the upper end of the stick. Try leaving the oil under the halfway mark and seeing if level continues to drop from there. Check oil 5 minutes after shutdown fully warmed.

It sounds like you have a worn out engine (rings) - however, a full fuel system inspection beginning at the tank is certainly in order if you do not know the state it is in.

Does it currently smoke? - please describe it.

Try posting in "Diesel Discussion" from now on. This is not the place to get a response.

chelsea's dad · #3 11-28-2013, 01:22 AM

don't know condition of fuel system. doesn't seem to starve for fuel but clear pre-filter is never over1/3 full.
yes it does smoke, all the time. really bad on warm up, bad when accelerating, not too much at idle after warmed up. sounds like rings.
i thought i was in diesel forum. sorry been a while since i have been on here.
what would process be for going through fuel system? once read about switching fuel lines to back flush debris out of tank screen, but nothing else to check.

thanks for the reply and any new info you might have.

whunter · #4 12-06-2013, 01:37 PM

This thread has been moved to Diesel Discussion.

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whunter · #5 12-06-2013, 01:48 PM

whunter · #6 12-06-2013, 01:49 PM

barry12345 · #7 12-06-2013, 06:54 PM

If engine is not leaking oil a quart every 150 miles it is pretty bad for these. What is the coolest temperature the engine has started at so far?

Also look to see if the engine has a return line from the vacuum pump to the intake and is there oil in it. The early 616 engines had that vent system I believe where the newer 616s vented the vacuum pump to the engine.

Of course that would not account for the car shaking like a dog with a bone. I probably would start off by doing a compression check on that engine.

Diesel911 · #8 12-07-2013, 12:28 AM

It would be nice to know the color of the Smoke and if it smells like Fuel or Oil or both.
If the smoke is puffing out unevenly some Cylinders or Fuel Injection is happening better on some than others.

You also did not mention if you were having a lot of Blow-by.

At 160k miles the Injectors are likely worn out. However, do to compression check first.

If you pull any Injectors and you look inside the Prechamber and the Carbon is shiny black insted of dried flat black a lot of Oil is being burned from somewhare.

If not the Piston Rings you can bring in Oil Through the Valve Stems/Guides/Seals.

Air leaks on the suction side of the Fuel Supply Lift Pump can also cause Engine Shaking.

t walgamuth · #9 12-07-2013, 07:07 AM

If the sound is like a jackhammer going on your frame I would probably be motor mounts collapsed and motor arm to frame being metal on metal. Simple fix. The high oil consumption is another matter. I cannot imagine one running good enough to get 30 mpg and use a quart in 150 miles. It must be pumping oil into the intake from a vac leak or something.

Diesel911 · #10 12-07-2013, 12:25 PM

Some Members have said that when the littl O-ring in the Fuel Supply/Lift Pump goes bad it sucks Oil from the Fuel Injection Pump into the Fuel Supply Pump and mixes it with Fuel and it is burned in the Engine.
That is another area of possible Oil loss with no exterior leaks.