Hi everyone,
I purchased a 1998 e300 turbo diesel a couple of months ago with 65,000 miles on it. The car ran so smooth at idle that there was no indication that it was even running. Now, 5000 miles later, it's running rough at idle and when stopped in gear.. The only thing done to it mechanically is the replacement of injector shaft seals. Does anyone have any thoughts about what could be causing this?

Also any recommendations for diesel fuel additive?

 

I am not sure what you mean by Injector shaft Seals.

The Injectors in the Cylinder head have a Heat Shield that seals them where they screw into the Head and they have Fuel Return Hoses on them.

The Fuel Injection Pump has a Throttle Shaft that sometimes leaks Oil and the O-rings/Seals can be replace.

As far as the rough idle goes this if often caused bay an Air leak on the Suction Side of the Fuel Supply/Lift Pump.
If your year has the Fuel Hoses that use O-rings to seal them that would be My first guess.
If you have a Fuel Heater it also has O-rings.

After that it could be the Fuel Suppply/Lift Pump (there is a rebuild kit) or I have read that the Plastic Parts inside of the Fuel Pressure Relief/Overflow Valve can fall apart and that messes with your Fuel Supply Pressure to the Fuel Injection Pump.

 

Hey i got a similar problem I own a 1996 E300d and it worked much like the mercedes mentioned above it ran nearly perfect except it had a leak on the pressure release valve and i changed the o-rings after i got the car to start i noticed it idled a little rough as the car warmed up on idle i start to hear knocking as if the first injector is not getting fuel once you hit the accelerator it works perfect the power is un-touched as before so i came to a resolution that the first injector may not work and i replaced it this did not solve the problem i really need suggestions please help another problem that i noticed since i switched the orings is that my temperature rises about 2 degrees more than before this may or may not be related

 

Hi
1998 e300 td, 47000 miles with FMSH


past couple of weeks ive noticed that it diesel knocks at around 1250 rpm, when you rev it the knock disappears. it runs great, no power loss, no smoke and starts first time. what I have also noticed is air bubbles travelling along the fuel lines on the pump. could this be the cause of the knocking? and is it an easy fix. I have read other posts on this site with similar symptoms is it a big job, im very handy with the spanners.


Thanks

 

Resolve the air issues, and you will probably resolve the diesel knock.