Marlene the wonder wagon has a dead miss at idle but makes the spec'd hp at full chat. Whassup with that?

Never any excessive smoke either. Hmmm.

Now that she's not connected to a fluid coupling, I'm beginning to understand why this car performs so much differently off-idle from SWMBO's 300D. It's just not hitting on all five ..hehe. I guess I couldn't feel the miss through the old torque converter or, something happened during the month she was on stands in the garage. Either way, there's a definite miss on one cylinder at idle and up to the point where there's boost and the engine is making power.

This weekend I plan to recheck valve adjustment and, barring any significant findings there, isolate the abberant cylinder and swap an injector from the 300D to determine if it is in fact, an injector.

Fingers crossed....

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Never a dull moment at Berry Hill Farm.

This'll be interesting. Leaky did something like that for a while before it wouldn't run anymore. Hope your experience turns out a lot better than mine.

Is there any smoke?

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Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References

Nothing unusual in terms of smoke...light haze on acceleration, no smoke at cruise. Oh sometimes a poof of black if I catch the turbo just right on a shift (still working on a way to replicate that reliably ). No white smoke, no blue smoke or, oil consumption either.

I honestly think she's been running like this for a year and I couldn't really tell because autotranny smoothed it out somehow.

It's like not enough fuel is getting to one cylinder at low throttle...

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Never a dull moment at Berry Hill Farm.

done an italian tune-up?

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1984 300D Turbo - 231k....totalled 11/30/07 RIP

I also have a dead miss. It appears VERY clearly at cold starts with rocking and gray smoke. The rest of the time, it *only* shows up between 1000-1800 rpm (Very clearly at 1500rpm) ans completely clearing up above that with plenty of power (Hence the good readings on my dyno test since it was started above 2000rpm.)

I know the cause of theis miss as air leaking past the PC seal ring of the #3 cylinder (Lowering compression). Since I am no longer in a place to do my own work, I have just been living with it.

maybe your injector swap will cure it. hope so -

all the glowplugs are good right? refer to cold start.

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1984 300D Turbo - 231k....totalled 11/30/07 RIP

You might think about running a thin wire down the prechamber to make sure it is not blown out at the bottom.
I am ninety nine percent certain that this was hte problem with my 1980.

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'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique

Timed the 300 yesterday and at right on 24 deg, it ran with a steady miss, as if a cyl was bad or low compress. So I just re-set it to where it ran smooth again and called it good. Will have to check it another way -not with the drip tube- and see where it's really at, but I've found in the last 25 years that some cars/engines just like to run 'outside of the box' and there's no explaining it.

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1984 300D Turbo - 4-speed manual conversion, mid-level resto

1983 300D - parts car

1979 300TD Auto - Parts car.

1985 300D Auto - Wrecked/Parts.


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"If you don't know where you are going, any road will get you there". Lewis Carrol

Leaking pressure valve holder seal (do a search on this). Didn't seal properly when someone replaced the o-rings on the pressure valve holders to fix a leak, probably.

This allows the pressure in the injection line to drop off slightly, so at idle the injector doesn't open, or opens late. At high speed and load (lots of fuel) it pops more or less normally.

Easy fix -- locate the missing cylinder and replace the seal. It's under the pressure valve body on the W123, I think.

If you cannot locate the miss by loosening injectors, it's something else.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Peter,
Thanks for the diagnosis. The scenario you describe fits Marlene's ailment to a "T." I have some things to finish on SWMBO's car before I can go back to the wagon but, I'll report on what I find when I get there.

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Never a dull moment at Berry Hill Farm.

Well, I finally had a moment to mess with Marlene yesterday. Now, after taking a 17mm wrench to the injector delivery lines, I know what a 'dead miss' is really like.

Unfortunately, at idle, her misfire is so doggone light that I was unable to determine which cylinder is the culprit by simply loosening the delivery pipes.

I guess I'll pull the injectors down this weekend see what I find.

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Never a dull moment at Berry Hill Farm.

Had the same problem trying to diagnose the miss on my 81. It was suggested that I use a stethoscope and listen carefully to the injector and the exhaust note. Try to locate the miss when you can hear the injector ping and the miss at the exhaust at the same time.
Not easy to do, seems the first and fifth fire at close to the same time. But I was able to isolate the miss anyway.
Haven't done anything that made it any better, but I was able to locate the problem.

So what the heck was it??? (slow night )

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

OMG! This thread is over two years old!

But, to answer, I've never been able to determine the cause of her 'hitting light' on one cylinder at idle. An injector rebuild shortly after this thread started didn't change a thing.

For the record I drive the snot outta this car, using it frequently as like a light truck to pull my trailer which may be carrying anything from a couple of sheets of plywood to my Bride's electric ranch buggy that weighs 1700#. If I'm driving it, the throttle only has three settings that are used: idle, cruise and full load. She loves pulling heavy stuff too...I swear Marlene runs better/smoother after working hard.

It's not a dead miss, loosening injector lines proved that. And, I can't imagine that it is poor compression because this engine starts easily in the coldest weather and does not consume any significant amount of oil (<1/2 qt in 3500+ miles).

I've just chalked it up to Mercedes weirdness and went on about my biz.

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Never a dull moment at Berry Hill Farm.