1991 300SD Rough idle
 

Hello. I have 1991 300sd and I have very rough idle when I start the car, but it runs well. Please let me know what this can be, it's new in Diesel industry.
Thank you

Sorry it's 1991 350SD
 

Sorry it's 1991 350SD

If it's just rough idle for the first 30-60 seconds, most likely you have a glow plug that's bad - although this usually means the glow light doesn't operate as usual (should come on for 3-5 seconds after you turn the key, and turn off when the engine starts). Might be something odd like a dripping injector that leaks a little excess fuel into one cylinder after shutdown, that makes it run rough upon cold start - but that's kind of a stretch. BTW, both your cars have the 3.5L engine that likes to bend rods & cost $6-$12k to repair. If you're not familiar with the problem, do a search on this forum (and the Web) for Mercedes 3.5L problems, oil consumption, oval cylinders, bent rods, etc etc...

;)

Frustrated
 

I am the owner of a 1991 MB 350SD and it still is running great at 190k and only burns 1qt oil per 1500-2000 miles.

I am afraid to post any questions about the car because everyone one ATTACKS the 350SD - even for simple things.

Yes, the car has a shaded history, however, there are many on the road that have been repaired or not affected.

I never see an answer or good suggestion about any 350SD - without a group of members ganging up to scare the poor 350 owner.

I am almost literally afraid to open a 350SD post.

Some of us own the cars and can't really do too much about it - just keep them running.

My 2 cents.

Sorry, dude. Great car, flawed engine. Fix the engine and then the engine is great too. BTW, 1500/miles per quart is not good. My 87 with 250kmi (and also an OM603 engine, like yours but 3.0L) gets about 7500/quart, and my other one (now wrecked) was in the 4000-4500/quart range (due to a leaky turbo, IMO). But a quart every 1500 miles, well, that's not a good sign... :( :(

That is within specs for burning oil - especially considering it has a couple leaks.

By the way the engine was repaired years ago

I don't think adding one quart of oil between changes is bad.

Things can't be giagnosed with just one statement. Maybe you have the magical diesel that doesn't burn oil. I'm very glad, but that isn't the case for all of us.

Take it easy man,;)

Hey I own a 350 too! Just replaced the injector pump because of a rough idle that was consistent at all engine temperatures.

The 350's are wonderful cars: tranquil, powerful, economical, and are very quiet on the highway in comparison to my 3.0 liter. I would never get rid of my 350! It even has ASD and a 12-disc trunk mounted CD system.

Feel better?:)

gsxr, don't you use Mobil 1 synthetic? No way dino oil could last that long in a diesel! Stop scaring bisric off!:p

My 3.0 liter goes through a quart right after 3K on the dot. The 350's oil gets dirtier faster. Down a quart at around 2K - 2.5K miles. So bisric, yours seems normal for a 350. Are you a lead foot when you drive too?

Thanks DslBnz!

It's unfortunate that these cars have problems. Mine was bought knowing the rods were replaced and the top of the engine was rebuilt. Bought it from a personal friend of mine who bought it for himself, but just had too many cars collecting.

It just seems that every post for that vehicle turns into "Hey man, dump it." It's frustrating. I thought we were all here to help one another. I may not post alot, but I am a frequent reader of the forum. I like to print out posts and read them later in the evening or while I am traveling.

Anyway, I appreciate your comments and bringing me back to my senses. I just have a couple questions/issues with my 350 that I am almost afraid to post.

What kind of mileage does your 350 get? Mine sat for many years and was just fired up again about 12 months ago.

Have you replaced your injectors? I have been thinking about mine to raise the mpg, but not sure. The car runs well, the timing is great and set to spec.

Anyway, thanks!

bisric,

I am sorry if the responses to questions seem less than helpful when you mention the 350SD. For some of us facing the unanticipated failure of the Diesel engine in an otherwise truly fine automobile has been a really traumatic experience.

You bought yours with the knowledge there might be an issue, and in the case of your actual car, knowing the problem was most likely addressed. For some of us, the problem was not known at the time of purchase and finding out Mercedes-Benz was not being forthright about the issue after the fact is not easily pushed out of our consciousness. So, sorry for the tone of many of my posts, although I try not to pick on the cars anymore because I recognize, had mine not failed I would still have and love it. And I would be a little richer too, as the experience was not without a financial penalty. But if I still had the car I would not appreciate everyone casting aspersions at it and, maybe indirectly, at me.

My 350SD was capable of about 25 mpg in combined city and highway (70+ mph) travelling until it got really cold or snowed. I do not think I ever got less than 20 mpg, even when it got sick. It would also break the rear wheels loose if I punched it from a standstill. It wore tires at a rate that was better than a W123, and, until it got sick, it never needed a quart between 3,000 to 5,000 mile oil changes using Mobil 1 15W-50. If the oil level light came on, I changed the oil. I bought a Topsider to make changing the oil on this car easier, so I never let it run for over 6,000 miles, ever.

Believe me, I wish I was one of the people with good luck. I really liked the car. So, sorry if the tone is too negative on the subject. I will try to avoid "piling on" in the future, and, if you have questions, please ask them. The forum, as you noted, is to share information, not to make owners of certain models feel like outsiders. Good luck, Jim

My '91 350SD had 215k on the original, somewhat neglected engine and still ran fine. But, for the most part, the engines are junk and for a prospective owner, I will tell them all day long not to buy the car. It simply isn't worth the risk of a $10,000 engine.

For current owners, all you can do is keep them running and hope for the best. And 1qt every 1500 miles is within spec but certianly not normal (I think MB calls abnormal consumption at 1qt every 800mi). My 300SDL with 300k on the clock was using zero oil at 4,000 mile intervals.

No problem! ;)

I currently average about 23 - 25 mpg right now. Winter is approaching, and the fuel is becoming mixed.

My injectors have not been replaced for 30K miles or so. They should last 100K from what I've read.

What's your MPG? Maybe you're getting bad fuel instead? When was the last time you changed the two fuel filters?

Enjoy your 350 while you have it, and, Jim I'm sorry for your prior loss. I'm happy that you are taking a fair attitude in light of the situation instead of how most people continuosly bash cars they don't know anything about.

Again, got to go to bed early tonight, so I can't respond anymore today.

:eek: :eek: :eek:

WOAH HO HO!

Your posting was so loud it woke me out of slumber! Dave, take it easy.

Hey I will admit I can get a little hot under the collar myself, but you just got to take it easy. Don't get so offended.

He was just sick of people telling him his car was a piece of junk(I can empathize with that), and so he snapped at you. This is Mercedesshop.com, the home of the chivalrous DIY'ers and MB techs. Let's prove our worth.;)