Car sat for about two weeks over the holidays. Drove around town upon return without incident. This morning 4F outside. Started right up with one glow cycle. But, in the early going, it was extremely sluggish....trouble even getting to 30 mph. After 10 miles or so, things improved considerably...could get up to highway speed. But still not as responsive as normal. And to top off my morning the horn doesn't work.

FYI leaking fuel thermostat was replaced a couple of months ago.

I will drive it home another 10 miles in a few hours, so we'll see.

Any ideas?

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

well it's an old diesel that needs to warm up. the cold outside makes things a lot slower. I personally think you're over worrying. I'd let it get up to operating temperature before making any judgements. you should also let it sit when it's that cold outside at least 3 minutes so the oil can circulate. It sounds like you're immediately starting it and going which is not good. I don't believe in letting diesels idle for extended periods because it's not good but 3 minutes is a standard rule. you also shouldn't shut it off without it being up to temperature because you'll cause condensation in your oil.

enjoy the ride and stay warm!

also if the issue persists its worth checking your fuel filters. you said it sits a lot so that may be letting condensation get into your tank which could be causing gunk to clog your filters!

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

Warmup Needed x2. When it's really cold, you have a few things working against you. The oil is thick and there's not enough heat in the cylinders to adequately vaporize the fuel.

Remember that in a diesel, the fuel is combusted by the heat of compression, but before it can combust it needs to vaporize. When it's REALLY cold out, adequate vaporization of the fuel in the prechamber can take a couple of minutes since the brutally cold air charge is working against the heating done by compression and the previous combustion event.

The oil being thick works against you too. Not only does it resist movement in the engine, but it prevents the turbocharger spooling easily. Adding insult to injury, if it's cold enough the fuel itself can begin waxing or gelling.

Try letting it warm up for a few minutes before taking off when it's really cold like that. It's easier on the engine and easier on your patience too.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

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

And use your block heater (if not doing so already).

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1991 300D 2.5 "Rocinante"
2002 Golf TDI "Teen Spirit"
--------------------
1984 300D
1966 Mustang I6 3sp
1985 Mazda RX-7 GSLSE
1982 Toyota Supra
1977 Datsun 280z
1971 Datsun 240z

Actually, I did let it idle for several minutes.

The car has been through seven New England winters with me and this behavior was unique. It wasn't the kind of slowness that one would typically associated with a cold engine. I've been driving OM602 cars since 2003 so am pretty familiar with how they respond to the cold.

Block heater has never worked.

Let it sit for four hours then drove ten miles. Everything working perfectly...including the horn. Weird.

It will be -7 tomorrow morning...we'll see what happens.

__________________
14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

You may have some fuel clouding due to the cold weather, but not enough to block the filters. Simply driving will eventually warm up everything in the tank and performance will improve. There was a recent thread on winter fuel additives, which is worth reading.

I was wondering about that...and wonder if the half tank of fuel I had in there was before the changeover to winterized diesel (although that was on 12/8, so I'd be surprised if the changeover hadn't occurred). Filled up the tank.

It's been this cold or colder before and I've never had an issue.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

+1 fuel clouding, that issue seems to be going around.

This is according to the guy who pumps fuel here(in Oregon we're too dumb to pump our own....), so take it for what you will.

Around here, the fuel stations mix the fuel for the weather expected in the next week or two, not just a switchover immediately to winter fuel that'll handle under zero immediately, as colder blends cost more. When a cold snap hits, buying fuel from a station that has a high turnover rate is important, and also making sure the fuel in your own tank is turned over is important.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

That makes a lot of sense. So I probably have a half a tank of fuel that is NOT prepared for the cold we're experiencing. Perhaps the half tank I added today will be enough to get me on my way tomorrow.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

I'd be inclined to add some antigel as well. Better safe than sorry and all that.

We don't get the cold temps like you guys get(15ish is about as low as it gets) but I still add antigel. Doesn't cost much, not much hassle, and it would only take once having a fuel system full of butter to really make me wish I had treated it.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

Absolutely. Put some Power Service in and drove it enough to circulate through lines and filters. Should be all set.

Surprising I've never had an issue in all these years.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

same here.
verrry sluggish for first 1/4 mile or so with minimal/no warm-up

perked up after driving a bit

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1991 300D

This is what you need to eliminate gelling and sluggishness....

Power Service Anti-freezer

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-- Chris

'95 E300, 216k miles, Silver Surfer
'05 E320 CDI, 138k miles
'07 S550 4matic, 69k miles

Gone but not forgotten:

'76 300D, 350k miles?, SOLD in 1995
'75 240D, 300k miles, SOLD in 1991

I have a gelling problem maybe once every ten years. I never use additives, so it's probably due to variable fuel quality.