My car has 182k miles on it and I would be willing to bet the injectors are original.

1) The car has a pretty good case of the hot-idle shakes - some of this is due to a low idle, I think. According to the tach, it looks like it's in the 600's somewhere.

2) Smokes a little - I can notice smoke at stop lights when there is a good tailwind and the sun is shining.

3) Average mpg ~ 24

I pop-tested all the injectors about 30,000 miles ago, and all had a good spray pattern and popped within specs.

Recommendations? Just adjust the idle and keep driving?

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cbjukraine
'84 300D

Do you have your own pop tester? If so, test them again.

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2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

no, it was a friend's. he made it with a bottle jack and some 617 junkyard parts.

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cbjukraine
'84 300D

Did you do any other tests besides the spray pattern test? If so what did you do?

There is quite a few threads where I posted a diagram of the stock Bosch Nozzles that have tiny passages drilled in the Pintel. Those passages get clogged over time.

There is also an extra test when using the Pop Tester to see if the Fuel is coming out of that central hole instead of around the Pintle tip.

You could also simply pull one Injector and inspect the tip of the Nozzle. If the Metal around the Pintel is all burned and eroded/undercut they have been in there a long time. If the erosion goes into the Pintle Hole the Nozzle is no good.

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84 300D, 82 Volvo 244Gl Diesel

As a general remark, related to this thread: I have never been clear on why a dirty injector would be more evident at idle on a hot engine than at other times.

Just wondering....

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

I don't have a clear answer for that and so far have not read one.
For me when I was rebuilding the Injectors I found that the Injector Pintel drilled passages were plugged solid with Carbon.

I also found that most all of the Injectors I had pulled at the Junk Yard were also plugged up.

In the Factory Service Manual it has that the passages are there for idle and low amounts of Fuel to pass through.

I assume that the plugging is partly caused by not doing periodic Diesel Purges to keep the passages open. Once solidly plugged I think the Diesel Purge Chemical is going to go around the plugged area just like the Diesel Fuel dose.

Also in the Factory Service Manual Bosch increased the size of the central Hole at some point. It could be that was done to decrease the chance of plugging.

If those holes were open the Idle Fuel is going directly down the center and focuses the spray directly at the Ball Pin in the Precombustion Chamber.
If the Fuel cannot go through the hole it has to go around the Pintel and the Fuel will be sprayed is less centralized and around the periphery of the Pintel.
When that is happening the Idle Fuel is not burning in the area of the Precombustion chamber it is supposed to and not being directed at the Ball Pin. (Fuel spray hitting the Ball Pin is supposed to get better atomized.)

For some as of yet unknown reason that had the effect on my Engine after about 20 minutes of driving around Town of causing the "hot idle shakes".

Rebuilding the Injectors took away the largest chunk of shaking. The next largest chunk of shaking was taken away after the Valves were adjusted.

So for me it was associating a cause with and effect. Injectors rebuilt a whole lot of shaking went away.

Note: The first Injector Nozzles I used were Brand X cheap ones made by 7Diesel. A year or so later I replaced them with Monark Nozzles.
Neither of the above Nozzles have the drilled passages like the Stock Bosch ones do. The 7Diesel has a skinny but undrilled Pintel tip (Bosio Nozzles are like that) and the Monark Nozzles use a "Facet" (a flat spot on the side) to deal with the idle and low amounts of injected Fuel.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

Thank you for that. It's the clearest explanation of the issue I have ever read.

Based on where I was before I read this, and on other things I have read over the years, many people are unclear on how the injector nozzles work.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Thanks.
I got the info on the Stock Nozzles from the Factory Service Manual. I have found that having the Service Manual is big help to me.

I have read quite a few places on this forum what the function of the Ball Pin is. And, previous to owning a Mercedes I did not know the Ball Pin was even down there.

The rest was observation of what happend before and after I rebuilt the Injectors and adjusted the Valves.

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84 300D, 82 Volvo 244Gl Diesel

Getting the idle speed right will really help with smoothing it out. If you are getting 24 mpg I would think it is in pretty good shape overall including the injectors. 800 rpm at idle is pretty universal I believe.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.