Rough Idle 240D - PeachParts Mercedes-Benz Forum

TX76513 · #1 07-21-2003, 08:50 AM

Ran across a 83 240 D this weekend and may have the opportunity to own for very little green but......when at idle this little 4 banger rocks under the hood. Inspecting the girl I noticed the maniflod gasket in the trunk and the Owner said he had the #1 piston/rings replaced by xyz mechanic. Once you move over 1K RPM's everything levels out and the car looks and run wells. What should be my fears with this car in reference to idle?

mickey mouse · #2 07-21-2003, 10:55 AM

If that was my car, I would check the valve adjustment clearerance. If upon seeing that is ok, with the engine running at idle, loosen the fuel lines at the injector one at a time and observe if any one doesn't affect the shake. If while loosening any one, there is little or no change to the shake, that cyl. has some issue with performance. If I found one that seemed week, I would pull that injector and check it for a good spray pattern. If you don't have the equipment to check injectors, just pull another one and swap the two. Do the loosen-the-lines test again and see if the problem followed the injector; if so,have the injector repaired. If all this fails to reveal anything, do a compression test. If #1 proves to have much more compression pressure, while the others are still acceptable, than I would have an explanation for the shake and drive the car for another 100 or 200 or 300K. That's what I love about these diesel cars. Milage is referenced by 100Ks. Again, I enjoy reading this forum. It really helps me sort out a lot of problems with my cars; as I am kinda new to the MB product.

#3 07-21-2003, 12:40 PM

The 240D has a black knob on the dashboard to the left of the steering wheel which adjusts the idle...I'd first twist this dingus this way and that and see how it affected the shimmy...you'd be surprised what a difference the setting can make.

#4 07-21-2003, 03:07 PM

My 240D had an idle that would shake your false teeth out, now it purrs. Stuff like fuel filters, and, ok, a new timing chain at 166k miles, made the difference. You can probably smooth out the idle without any major expense.

#5 07-21-2003, 03:30 PM

My only question is why only having #1 cylinder worked on? I'd go for a complete engine inspection. Do everything that has already been suggested, and I would try to find out what the oil consumption is like on the car.

TX76513 · #6 07-21-2003, 08:27 PM

All good answers (and even some I thought myself) - the onwer out in the country doing some shade tree mechanics - and didn't feel good about some of the answers. Have all the good stuff to do a complete test (compression/vac/etc) - but it was Sunday afternoon - just took a drive to "look". The owner said on the phone it was perfect - but quickly recanted when we drove up in the SDL. Without knowing about the quirks of a 240 this forum was the best querry. I could probably part it out for the $650???? jk