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83 300TD Rough Idle
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Posted 5/11/2016 2:41 PM
New user

Date registered: May 2016
Location: Chatsworth, CA
Vehicle(s): 1983 300td, 1981 300d
Posts: 1

83 300TD Rough Idle

Hi all,
Got an 83 W123 wagon with 342k on the clock. 617.952 turbo engine. I have gone through the issue of a shaking engine, and adjusted the rack damper to fix that. (Along with new injectors, regular valve adjustments, etc.) THIS is a different issue. The engine vibrates at idle, hard. It is much worse when in gear and stopped, because of the load from the auto trans.
More Detail: This is not a consistent issue. It is usually worse when the engine temps are higher, such as after getting off the freeway or driving around town on a hot day. On cool mornings, it will usually idle pretty smooth even when in gear and stopped.
I have no power issues above idle. It has a rebuilt turbo, and the 0-60 time is pretty close to the factory spec, and other than the bad idle the car runs good. I get 25 mpg on the highway. However, the exhaust valve on the #5 cylinder has stretched to the point that the adjuster nut is run all the way down and i cannot get anymore adjustment out of it. It may be stretching under high heat conditions to the point where it won't close, thereby rendering #5 down on power, causing the rough idle.
I know that a bad idle can be a symptom of an injector pump going bad, but could one or more stretched or sticking valves cause this issue as well?
Looking for any insight anyone might have on this.

Edited by Nickp 5/11/2016 2:43 PM
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Posted 11/19/2016 6:16 AM

Date registered: Apr 2006
Location: Georgia
Vehicle(s): 90 300GD "Thundering Turtle II", w/ 603A turbo
Posts: 3118
Re: 83 300TD Rough Idle

Simple first:
How are your motor mounts and transmission mount? When cold rubber is harder when hot it is softer. Put your hands on the valve cover and try to rock the motor back and forth. If it moves a lot mounts are shot. Easy DIY.

Have you done a Diesel Purge on her. At least once a year. Here is how and a great web site if you have not gone here yet.

Main site: http://dieselgiant.com/mercedes_diesel_maintenance_tips.htm


Edited by Inkblotz 11/19/2016 6:18 AM
#234507 - in reply to #232312
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