rough idle
 

would the air filter being semi-plugged cause rough idle and vibration?

I think t would have to be fairly plugged to cause vibration, but a plugged air filter will cause the vehicle to run rich(too much fuel vs. spark). Rich or lean conditions can cause rough idling.

There are innumerous things that can cause a rough idle.

Your profile shows a 83 300D. Rough idle could come from the valves out of adjustment. When were they adjusted last?

The fuel injector rack also has a part, a small brass piece whose job it is to dampen the rack. These often need replacing on older cars.

Clogged injectors can also contribute to a rough idle .... as well as bent or bad valves, bad fuel injector pumps ..... also a bad engine mount ..... etc.

How many miles?

Haasman

rough idle
 

where would i find the small brass piece. i am diesal ignorant so i have to do one thing at a time. have not adjusted valves since i got the car 2 years ago. car has 254,000 miles. is there anything i can put in the fuel to help unclog injectors. don't have a garage anymore so what's best going through the tank.

The brass piece is found on the right-side of the injection pump, the head of which looks like 15mm bolt with a smaller one inside. It has been over four years since I have done one so my recollection is a bit fuzzy. You might also post this question on the Diesel section of this forum.

I used to use Redline fuel additive regulary with fill-ups. Also Diesel Doctor or even Diesel Purge are good if you think you might have an algea build up.

Regarding the valves- they are supposed to be adjusted every 15k miles. From what you posted I don't see how long in miles but two years may be a long time. Diesel engines are very sensitive to a good valve adjustment.

Hope this helps, keep us posted,

Haasman

thank-you for your help. i'll keep you posted