300Dt runs like crap....
 

At low RPMs, my benz runs like hell. It shudders (loudly), has almost NO power, wants to die, and sometimes does. When I take off from a light, I basically have to push the pedal to the floor to keep it from dying. It was recently repaired, as my fuel lines were awfule, but everything was replaced as was the fuel filters. I got a new battery, the oil was changed, and the valve cover gasket was replaced. I did notice however, that the drivers side motor mount apears to be almost totally gone. Would this make the car run so poorly, or is it something else, like ****ty timing? It only recently started doing this (about a week ago), and its been a month since i had it worked on. What do you gifted individuals perceive the problem to be?

P.S.: up until may this car had been sitting all winter....

Check the clear in-line fuel filter -- I'm guessing it will be black.

Sounds like plugged fuel filters to me from crud in the tank. You didn't run it low on fuel just before this started did you?

New filters are cheap.

Broken mounts will cause excessive vibration, but not preformance problems.

Peter

have you removed the tank strainer and cleaned it?

The filters under the hood are less than a month old, and the clear one looks great, so I don't think its those filters. as for the tank strainer, i wouldnt know how to clean it. Any advice/tutorials on that is welcome.

BTW, I just started using biodiesel when the gas station I go to switched to it a few weeks ago. could this be part of the problem? I bought some fuel injection cleaner for diesels and it didnt make a difference.

i suspect you have the sedan..correct? well when you have the tank level guage reading on R.. back the car onto ramps, chock the front wheels... get a bucket or something to catch the fuel left in the tank.. notice the large nut with a smaller nut and a fuel line going into it, thats the tank strainer.. usually you can unscrew the smaller nut with the fuel hose on it and the big strainer will come with, if not remove the small nut with hose and use a 46mm socket or channel locks and remove it..

other members chime and make any corrections if i had typed some incorrect info, im certain that is the proper procedure.

Good luck getting channel locks on there. There's some kind of metal trim in the way that makes it nigh impossible, on my car anyway. An easy way to check is to take the line that comes out of the tank and disconnect it where it clamps on to the hard line that runs up front. If fuel streams out you don't need to go any further.

You could also try switching the supply and return lines, and see if that helps.

Correct me if I'm wrong, but a Bad engine mount could lead to enough shaking/vibration to make the car run terrible. Also mentioned new valve gasket, does this include a valve adjustment?

If no valve adjustment I would do the adjustment BEFORE messing with the fuel tank. I would also disconnect the primary fuel filter and see if fuel pours out the fuel supply line, before I messed with the tank. Just my 2¢

My '83 300D too
 

My '83 300D runs like this too.

I've cleaned the tank strainer. Replaced all the filters and rubber fuel hoses with Viton. Performed a valve adjustment. Cleaned the banjo bolt, associated cable, and switchover valve. My motor mounts appear good.

I replaced the old style (silver) IP rack dampener bolt with a new (gold) bolt. I adjusted it - but the best setting (least engine movement) was for it to be screwed all the way in. But the engine still doesn't run smooth - at idle or when accelerating.

has the primer pump been updated?

Yes, my 300D has the new style primer pump. Does that cause problems?

i was rather thinking if it was the old style it might be leaking air / fuel.

rack bolt all the way in is usually a sympton of the old style that got worn down. i would try loosening your new one outwards about half way then turning slowly inwards.
good luck

temporarily....

Change the secondary filter..........again.

The biodiesel could have well disloged accumulated crud in the tank and this stuff will definitely plug the secondary filter.

The fact that this situation came on suddenly further points to filters rather than a deterioration of hardware.