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Discussion Starter #1
It's been a couple of years now that my 82 240D with approx. 240K miles has a rough idle problem which manifests mostly after a long drive. It got to the point where the engine would start to stumble. It then progressed into a shuddering upon acceleration but smooths out at around 45 mph. I did a diesel purge a couple of weeks ago but only used one bottle. The leftover purge was quite dirty with some pieces of floating debris. I changed the fuel filters immediately post purge. The shuddering and stumbling improved visibly but are still there. There is no excessive smoking, fuel filters have been changed regularly and car runs fine otherwise. I have noticed over the past couple of weeks that the car takes a few seconds of cranking to start. Starting used to be immediate. Does all this point to an injector problem or could something else be amiss?
 

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1984 300D
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The Hot idle Shaking can be cause by a number of things.

When I had that adjusting the Valves and rebuilding the Injectors too away >80% of the issue.
The rest was taken care of by replacing the Motor and Transmission Mounts and dealing with a Air Leak.
You don't have one but on the Turobed 5 cylinders there is an special spring loaded screw that will take away some of the Shaking. The updated gold colored one has a stronger spring in it. But, in my case it did not help until I did the other stuff first.

So the Valve Adjustment is free if you do it.
If when you pump on your Hand Primer it leaks Fuel that can be the source of an Air Leak.
You can Simply replace the 2 sections of Fuel Inlet Hose with regular 5/16"Id Fuel Hose from the local Parts store as it is rated for Diesel Fuel. That will take care of Air leaks on the Fuel Inlet side.

As for the Injectors if they have never been replaced the Nozzles inside of the Injectors are good for about 100,000-125,000 miles before they are worn out.
Also during that time the pressures that they open at tend to drop and are uneven between each Injector (out of balance).
Lastly the Stock Injector Nozzles have a tiney Hole drilled down the Center of the Pintel/Needle and another inside crossed wise. On My Car and most have pulled from the Junk Yard those passages were entirely packed with Carbon.

I also don't think that once they are packed solid a Diesel Purge is going to was it out.

The little drilled passages are there for the Idle Fuel. So having them plugged up has an effect on the idle.
 

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Discussion Starter #3
Thanks. That's very informative. My pump does leak. As far as valve adjustment- last time I did one it did not improve the idle situation but I'll do one again as I'm due. Based on mileage it seems that I need injectors.
 
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