300SD Rough Idle - Mercedes Forum - Mercedes Benz Enthusiast Forums

Diesel Discussions Only diesel topics should be posted here.

Thread Tools Search this Thread
Old 07-18-2006, 09:38 PM
Thread Starter
Join Date: Jul 2006
Posts: 38
Default 300SD Rough Idle

Just purchased an 81 300SD Turbo Diesel

The engine idles with extreme vibration. as soon as you touch the pedal to bring it to about 900 RPM it smoothes right out.

It dosent seem to be missing at idle, just really vibrating.

the guy i got it from said it idled smooth before he parked it 2 years ago.... so who knows if thats a lie or not..
motor mounts maybe?

I changed the primaryfuel, main fuel, oil, and air filters today - didnt help at all.

I wound up just raising the idle a bit so the car is more driveable

any thoughts are greatly appreciated!


[email protected]
Reply With Quote
Old 07-19-2006, 10:21 AM
Join Date: Aug 2005
Posts: 86
Default RE: 300SD Rough Idle

Motor mounts....definitely. You probably have/had and oil leak that soaked the mounts w/ oil. That turns the rubber to mush. It's not a bad job to replace them, I'd do the dampers too. Also check the trans mount.
Reply With Quote
Old 07-20-2006, 12:47 PM
Thread Starter
Join Date: Jul 2006
Posts: 38
Default RE: 300SD Rough Idle

Motor mount was it! the left oe was shot got it replaced and now it idles smooth!


Reply With Quote
Old 02-12-2007, 11:05 AM
Junior Member
Join Date: Nov 2005
Posts: 16
Default RE: 300SD Rough Idle

I just want to chime in here and say I just tried replacing the motor mounts on my 1984 300D. I did not find it to be so simple a job. There are three bolts to each mount. One bolt goes to the engine and is accessed from under the car. The other two frame bolts appear to be accessed from the top. I was never able to find a way to get to the frame bolts. They are about 2 feet down from the top of the engine and the top of one of the bolts is blocked by the arm that comes off the engine.

I've done tons of work on this car (valves, injectors, veg-oil)and this is only job that I couldn't finish. I ended up taking mine to a mechanic. [&o]
Reply With Quote

Related Topics
Thread Thread Starter Forum Replies Last Post
E300 Running rough, real rough alchan Diesel Discussions 5 04-06-2014 09:24 AM
Loping, rough running, rough idle, missing on one cylinder, almost no power, spark plugs WaBenzer Mercedes C Class 3 08-26-2008 06:41 PM
SLK320 AMG 2003 rough idle Bunnie Mercedes SLK Class 2 12-10-2005 03:52 PM
97 e320 rough idle jon98909090 Mercedes E Class 3 01-20-2005 01:55 AM
rough idle 92 400SE smk51 General Tech 1 07-20-2004 03:25 AM

300, 300sd, adjustment, benz, front, idle, idles, left, mercede, mercedes, motor, mount, mounts, photo, rough, sd, throttle, valve

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Featured Sponsors
Vendor Directory

All times are GMT -5. The time now is 06:22 PM.

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.