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  #1  
Old 03-15-2006, 05:12 PM
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Join Date: Mar 2006
Location: North Texas
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bad idle at start up but seems fine after running

I have a 1981 300D which I love. It was running really sluggish so I ran diesel purge and changed the filters as instructed. It has a greater "zest for life" now. However, in the morning, it starts but idles rough and seems to be knocking a lot. After about 5 minutes of driving, it settles down, idles well with much less knocking. I had read the posts about similiar behavior and folks recommended Red Line Diesel Catalyst, etc. No leaking fuel lines and the fuel in the prefilter is nice and clean. I don't want to do anything to harm the old gal as she is my only means of transportation and very reliable.
OBTW, I live in Dallas, so its been nice and warm (50s and 60s in the morning) lately.
Any ideas?
Thanks,
Clint

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  #2  
Old 03-15-2006, 09:57 PM
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Sounds like it could be a glow plug not working well or at all. At those temps the car should start ok with only 4 plugs. Check the resistances and replace those that are bad.
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  #3  
Old 03-16-2006, 10:26 AM
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I had a similar issue with mine and after adjusting the valves yesterday it has smoothed out considerably. What I discovered is that four intakes and an exhaust valve were way to tight which even seemed to cause minor collisions between a piston and valve until it warmed up. A horrible sound at best !
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Old 03-16-2006, 12:27 PM
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Quote:
Originally Posted by Wiz3D
...four intakes and an exhaust valve were way to tight which even seemed to cause minor collisions between a piston and valve until it warmed up...
They would have to be really 'tight' to interfere with the piston... More likely the valves did not close completely, and the loss of seal lowered the compression and resulted in poor combustion and running.
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Old 03-16-2006, 01:31 PM
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Do you have a bunch of unburned diesel smoke when you start up - then it goes away within a minute or two on the highway?

That might be an injector(s) leaking fuel down into the cylinder(s) after you stop the car. Then when you start up there's a lot of extra diesel fuel in the cylinder that needs to get burnt/cleared out before the engine will run smoothly.

Not sure what the resolution would be on that - maybe diesel purge - maybe injector rebuild.

Ken300D
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  #6  
Old 03-16-2006, 01:36 PM
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My SD will skip and run rough after its started. In my case after eliminating a few things I think its either a weak injector or a weak cylinder.

It could be air leaking into the system as well. If you have covered the basics like making sure the valves are adjusted I'd pull the injectors and have them tested.

Also if you have the old style hand primer pump you may have an airleak, switch to the updated one.

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