Hi all
Diesel guy here who went to the "dark" side

I bought a winter beater 1995 m104 w124 wagon. No records, it's the usual deferred maintenance junker. The price was right and I didn't want to expose my sdl to road salt.

I'm not familiar with the M104, but I am mechanically inclined.

So far love the car. But I've been getting 13mpg city (suburbs). Looking online I've seen people talking about ranges from 15-20 mpg city.

Is my mileage normal or low?

The car has a slight shake and maybe a slight missfire at idle. That could be the motor mounts though.
When accelerating and at speed the car is smooth as silk.

The car has the updated wire harness.

So far I've changed the plugs(copper non resistor plugs) and the air filter and gave it an oil change.

My to do list is
clean the maf
Clean the throttle body
Check the vac lines
Change the O2 sensor

What are areas in the engine can I test/look at?

Thanks for any input.

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1974 240d
1983 240d -sold
1989 420sel with om606
1994 s350 turbodiesel - sold

diesellac, you changed the spark plugs so you should have noticed if any looked different than the others ... which would indicate fouling due to: 1) not firing properly as a result of a faulty ignition wire, faulty spark plug connector or faulty top-mounted coil, or 2) damaged piston rings allowing oil into the combustion chamber ... not likely.

Engine mounts are a common replacement items, especially if the engine has high mileage. I had a 1995 E320 engine that developed no compression in No. 1 cylinder. Not sure what caused that sudden situation, but as you might expect there was a significant shake at idle. I junked that car with 200,000 miles instead of throwing money at the problem.

If you lack service records for this vehicle consider replacing the fuel filter. Also, replace the air filter.

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Fred Hoelzle

This is just my opinion, so keep that in mind -

Since this is just a winter beater, it might be cheaper just to live with the 2mpg economy penalty and move on to something better next year. Throwing parts at the problem can get expensive fast - way more than 2mpg over the course of a season. Your driving style and your mood can affect your fuel economy far more than you may realize, if you're used to diesel, you may be expecting more than that car is able to deliver.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

Get a compression test gauge and do a test across the cylinders both dry and wet to see if your compression is even and high enough. Next step would be a leak down test to get better idea. You can find videos on YT on how to do this and it doesn't take a long time to do.


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Diseasel300

Honestly that was my plan when I bought the car. Im looking for a nicer s124 to drop a om606 into.

I was just wondering what are some cheap items I could look at. Maybe learn a bit about MB gassers. Eh I'm probably better off sticking with diesel lol.

I can live with 13mpg.

__________________
1974 240d
1983 240d -sold
1989 420sel with om606
1994 s350 turbodiesel - sold

Ferdman

The last cylinder spark plug was a bit wet, but the last knucklehead didn't torque it down completely. It was pretty loose.

Ill get a fuel filter.

And I got a compression gauge set, ill look into that later

__________________
1974 240d
1983 240d -sold
1989 420sel with om606
1994 s350 turbodiesel - sold

Seems low to me, since I could squeeze 24mpg out of my '94 E420. What about the ETA? Was it replaced also? The wires in mine were bare...all the insulation had fallen off. The mass air sensor on mine needed replacing too... tried some CRC air flow cleaner first, but didn't seem to help, but might be worth a try, since it is significantly cheaper than a new sensor. Good luck!

__________________
It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

You should be in the 18 to 24 mpg range, check fuel pressure regulator, common to leak gasoline into the vacuum line, next check air mass meter, either for codes or substitute a known good one those two items are usual suspects , car should run 20-50w oil, fuel pressure runs at 55 -58 psi,check thermostat should run just above 80c to 105 c normal range, tires pressures run 30 psi,

diesellac, a wet spark plug indicates that it is not firing and igniting the fuel/air mixture. Recommend replacing the spark plug connector under the Cylinder No. 6 coil pack. It's also possible that coil pack is bad.

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Fred Hoelzle

winter fuel gets worst mpgs too.I stuck on champion spark plugs,I tried all others,and they would carbon foul with regular gas.Champions don't,I run regular fuel in the cold months.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

I haven't had much time to work on the car lately. But I think I found the culprit.

I took a look under the passenger side floor mat to look at the O2 sensor cables. water somehow got into the passenger side floorboard... one more problem to investigate. the water corroded the 02 wiring even disintegrating one of the female pins, disconnecting one wire.. For now I redid the wiring and the car is running MUCH better.

__________________
1974 240d
1983 240d -sold
1989 420sel with om606
1994 s350 turbodiesel - sold

I guess this is one of the reasons I got the car so cheap.

The motor is much quieter. The car moves much better from a standstill. no more misfire, and no more backfiring.

I'm definitely a happy camper. I just tanked up, Ill update with mileage after I go through the tank.

thanks for all the help.

__________________
1974 240d
1983 240d -sold
1989 420sel with om606
1994 s350 turbodiesel - sold

these are a great car properly sorted out and give 25 plus on the highway with great speed and power, sometimes nearly 30!

Ive had two..now have a w211 and its got less power (less torque) and uses more fuel!