Tough Diesel Idle problem - PeachParts Mercedes-Benz Forum

Jim Sutton · #1 05-15-2012, 09:15 AM

I have a pretty unique problem with my 1984 300sd that has had me occupied for about six months now.

I have read quite a bit about this but have not found that anyone else has seen something like this. I am now at the point that I need some serious help or will need to break down and say I can’t fix it and bring it to a mechanic.

I have owned my car for three or four years now. I have worked on it continuously fixing all the little things that break on these older cars. It ran ok, but last year I acquired a motor and trans, so I decided to rebuild both of them and swap them into my car. I take quite a few long trips with this car so I hoped to improve my reliability.

Here’s my problem:
When I take the car on a extended trip (20 miles or more), it develops a problem at idle. Almost like one cylinder is not firing. The car rocks, but stays running. Give it some "gas" and all is well, although the car does not feel as peppy as before. Let the car sit overnight and start it in the morning and the engine idles smooth again. Any ideas what this could be??? If you have an opinion, no matter how wacky it may seem, I am interested.

Let me share what I can about the car.

Valves – Adjusted properly. Timed correctly.
Compression – on a cold engine, all approx 380
IP – timed to 24 BTD with drip test.
Injectors – Monarch, purchased last year. I pop tested each and balanced to between 133 and 137 bars. New heat shields.
Run WVO, two tanks heated.

Hope you guys can help with this one. Thanks so much.

Jim