1991 E300 2.6 rough idle problem
 

Greetings

I recently purchased a 1991 e300 with a little less than 100k mi. It's in great shape, but idles terribly. This occurs at cold and warm tempuratures, but actually seems almost worse at warm temps. I don't really have a Mercedes specialist in my town, so I took it to my regular mechanic. He tuned it, cleaned injectors, and did all the "normal" things, but the problem is still there.

I would appreciate some advice from members who have dealt with this.

Thanks,

Roger

Rough idle
 

Roger,

Check motor mounts.

Big contributor to rough idle in 124s and mechanic not familiar w/MB may well not consider this.

One on each side of engine; on a '91 they are likely due for replacement unless your records show that this has been done recently.

Most forget the distributor rotor hidden under the front cover and cap.
Have seen many totally burnt away.

Check your OVPR fuse too. Remove it and check the date on it. If it is origonal...get a new one....$90.00 ish.



.

Has it always done it (since you bought it)? Does it seem to idle consistantly, but shake the car or is the idle unsteady? If it idles well but shakes, motor mounts are a likely reason. Cleaning injectors is a dicey project. How did he do it? Did he test them on the bench and observe spray patterns? If not, you could still need new injectors. I did a lot of work to mine and when I changed the injectors it made the biggest difference. When it is warming up the fuel enrichment helps with more fuel but at low idle you don't have the extra fuel. You have to ohm the spark plug ends as they go bad. It could be a lot of things. MHO only. Good luck.