My '87 300 D-T has 45,500 original miles on it, is in pristine condition, has had all scheduled tune-ups, had the oil changed every 3,000 miles, and uses no oil. Two years ago, when traveling up north during the winter, the engine began to miss and it spewed blue smoke when it was about twenty degrees Fahrenheit but the miss and the smoke disappeared when I increased the RPM's. During warm weather, it always started flawlessly, that is until about 6 months ago, when the engine began misfiring no matter what the temperature was outside but only when during a cold start. My certified Mercedes factory trained master mechanic said it was one of three things: clogged fuel filters, bad glow plug(s), or bad fuel injectors. One by one, he ended up changing all three but the engine still misses! He said the valves were self adjusting so that apparently isn't the problem and the blue smoke comes from unburned diesel fuel but disappears when the cylinder(s) begin firing so the rings are good. I've searched previous posts and most point to bad glow plugs but since I've had new ones installed, that cause has been effectively eliminated. Any suggestions would be greatly appreciated!

Virginia Dude, thanks for your input. I do the simple stuff such as brake pad replacements, oil changes, fuel/oil/air filters but leave the specialty work to the mechanic. I don't believe he did a compression and leakdown test yet and have no idea if he checked the glow plug controller but I'm going to ask him. He put a multimeter on the original glow plugs and although they showed good, he suggested to change them because he said that was the normal cause of a cold engine misfire. Although his credentials are good, from his past performance, I'm beginning to seriously doubt he has sufficient knowledge to fix this problem. One point of clarification. Once the engine starts and I increase the RPM's to get all cylinders firing, she purrs like a kitten all day long so warm engine starts aren't the problem, only cold engine starts. I'm going to take your suggestion to my mechanic and if he balks, I'll find a new one. Thanks!

Skip,

I believe the time frame your car was manufactured in was a period when MB had a problem with the Viton material used for the valve stem seals. I know it was such a problem on 190E's of that time frame they were replaced regularly, free of charge, even after the warranty expired. When these things fail, they can let engine oil enter the intake manifold whenever it is below atmospheric pressure.

In a turbo Diesel intake vacuum only occurs when you are idling and starting. This is inconsistent, however, with your report that you are not burning any oil. Smoking and missing at idle, following a "cold iron" start and assuming you spend most of the time with engine running with the engine under load (not idling), will not consume that much oil yet show a plume as the engine combustion temperatures are lower then and incomplete combustion of the Diesel fuel is common. So any added engine oil will also be unlikely to burn completely, and a Diesel at idle warms up very slowly compared to under load, so leaving it idling after a cold start will show the problem longer (and consume more oil).

Enough oil leaking into the intake manifold to cause a bit of blue smoke at start up can also develop a carbon build up on the intake valves that will interfere with proper valve function. This can lead to other problems like poor valve seating and lower compression, that show as poor starting, rough running as well.

Almost any other form of degradation of the combustion characteristics is cured by new injectors, valve adjustment or an "Italian tune-up." In some cases the prechambers can be damaged or clogged with soot from bad fuel/combustion and require replacement. Problems that have advanced to the point of damaging the prechamber ball pin, or clogged the vent holes show more extensive running problems (don't go away when you get beyond idle speed).

So, maybe you need to have your mechanic take a look inside the intake manifold and view the back side of the valve poppets and stems. If he changed the injectors he should have shined a flashlight in the hole and performed a visual examination of the condition of the prechamber ball pin, and anything else that is visible. Other than that, I cannot offer much of a suggestion. Good luck and I hope this helps, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Thanks Jim! Between you and TheVirginiaDude, I just received an eye opening education and I'm going to grill my mechanic this week. I'm getting a very uneasy feeling that since new fuel filters, glow plugs, and fuel injectors haven't fixed the problem, we're talking about a potentially serious and costly fix over and above the $1K I've already spent. If that's the case, although I hate to part with her after all these years, I'll probably be forced to just because of economics. Thanks for your input.

Skip,

Don't overreact. The valve seal fix is not likely to be expensive as, since it was such a problem during the mid '80s, MB developed a procedure used by all the dealers where the job is done without taking the head off. The parts are a few bucks per seal (check Fastlane), and the labor is not a whole lot more than the change of valve springs or something that gets the camshaft out (maybe twice the hours for a valve adjustment on a W123). The previous owner of my 1988 300E had it done in Utah at a local independent MB service guy for under $130.

Even the prechambers are not likely to cost what you have already spent and they are much less likely, based on your description of the problem, to be the culprit. I hope I did not scare you as the intent was to let you know there is a potential solution other than tearing the engine apart, that was not likely to cost a fortune.

Keep the faith, the chances are your car is not suffering from a terminal malady. Good luck, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Jim,

Thanks for going more in-depth. I was visualizing a major engine teardown but if the situation isn't that dire, will keep her for another decade or so. One question: Do you believe that repairing the cause of the engine smoking, which is only visible on an initial cold engine start, would also cure the engine miss or do you think we're dealing with two separate problems? I know that an oil burning gas engine can cause an engine miss by fouling the spark plugs but can the same thing happen with a diesel that uses glow plugs? And if your answer is yes, this makes me wonder why my mechanic didn't notice oil fouled glow plugs.

Skip, I went through something like this with my 99 E300 at about 40K miles. The dealer mis-diagnosed my cold startup problem and replaced all the injectors. When that didn't fix it, I took the car back in and they replaced all the glow plugs. That fixed the miss, but there was still a bad nailing in one of the cylinders for several hundred miles. Turns out one of the injectors was bad out of the box. Of course, the dealer always expects good parts so they don't test them first. So if the glow plugs test good, you may want to have another look at the injectors.

__________________
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

Rick,

Good point. When you say you had a "bad nailing" for several hundred miles, did you hear a noise similar to an engine or rod knock when you accelerated? Two days after I had the new injectors installed, I punched the accelerator to see if there was any change in acceleration and I heard what sounded like a rod knock which I had never heard before and it was unnerving. When I backed off on the pedal, the knock disappeared. You may be onto something; a bad new injector. Thanks!

Skip

Skip,

Diesel fuel ignition and combustion is not the same for all Diesel engine designs. In broad terms there are two main kinds used in automotive applications, the units with prechambers like your car and the bulk of the other Diesel cars in the USA (called indirect injection because the injector squirts into the prechamber and not the volume on top of the piston), and the new, direct injection styles where the fuel is injected into the volume bounded by the piston top, the head surfaces and a small measure of the cylinder bore in the block.

In your engine the glow plug heating element is inside the prechamber as well. The prechamber is "connected" to the volume above the piston by an array of small holes. As the piston moves up in the compression stroke, the volume inside the prechamber is pressurized by air rushing in through these small holes. At the point of injection the compression of the total volume of the air charge is at a level high enough to provide a temperature that will self ignite a thoroughly atomized stream of Diesel fuel. This stream of burning, hot gasses shoots back out the little holes and continues the burning process in the compressed air volume above the piston and outside the prechamber.

This concepts provides some control of the explosive forces of the ignition event, sort of spreading it out over time a little bit. It reduces noise and vibration, but adds particulate emissions, and reduces efficiency.

If you add to this event some blobs of engine oil, not well atomized and arriving with the charge of air coming through the intake manifold, you can imagine they will not be easily passed through the prechamber vent holes in the compression stroke. As a result they kind of "lie in wait" for the flaming hot gasses shoot out after ignition in the prechamber. If there is enough of a volume, of sufficiently large droplets, they snuff out the flame front rather than keep it going. This will lead to those misses and a burp of blue or even white smoke. As the engine heats up, the engine oil being drawn into the combustion chambers gets better prepared to burn and the bluish color begins to diminish. At load the turbocharger pressurizes the intake manifold and the path to suck liquid oil into the intake manifold is converted to a path to have air from the intake, pressurized by the turbo, squirt into the valve cover. This air adds to the engine blow by volume and can lead to oil being dragged into the intake air filter.

So the simple answer to your original question is, yes, anything other than what was intended to be in there can cause misses and smoking. Engine oil is not intended to be in there in a measureable quantity.

As for the glow plugs not having oil on them, they are shielded by the prechamber vent holes, which do not promote admission of stuff of a density higher than air, and, once the engine warms up the temperatures inside the prechamber will be high enough to burn off most anything combustible. At those temperatures engine oil would burn off quickly.

The fact that the oil arriving thereafter, with engine under load, comes through another path where it is much better prepared to be burned (it is intended to travel through a couple of paths to remove droplets of significant mass in the valve cover and the cyclone separator in the path to the intake manifold so only vaporized oil and other gasses make it into the intake manifold) adds to the probability the glow plugs will not get wet like a fouled spark plug.

Modern Diesels with direct injection achieve control over the ignition/combustion event by electromagnetically activating the injectors, which draw fuel from a highly pressurized header (called a common rail), and go through a series of openning and closing events per power stroke. The quantity of fuel, and its injection sequence is "designed" to achieve the best possible compromise of emmisions, noise and vibration, power output and efficiency for every given load and transient condition. Thus the "CDI" designation for Common rail, Direct injection and Intercooled on the new MB units.

Hope this helps, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Jim,

I regret not knowing about this site prior to taking my car in to be fixed because had I possessed the knowledge I've received from you and other helpful and very knowledgeable people today, I have no doubt my car's problems would have been correctly diagnosed and repaired by now. I really appreciated your in-depth responses. They've shed a whole new light on the situation and I now feel sufficiently armed to ask my mechanic intelligent questions and know when he's just shooting in the dark. Thanks again! Skip

If the smoke is definitely blue and hangs, it's oil smoke. If it's white and reeks of partially burned diesel fuel, you have a glow plug problem, possibly along with a valve stem seal problem. The contacts in the relay have been known to burn, causing poor current flow to the glow plugs, hard start, and white smoke/miss until the combustion chamber heats up.

Bad valve stem seals with give about a quart in 1000 miles oil consumption, possibly more.

If it starts right up, you don't have compression problems.

If you have very little oil consumption, get the relay checked out or replaced before getting excited. There is NO WAY you've worn that engine out yet! It doesn't even have enough milage to cause the head gasket to fail, the first usual problem. I have 179,000 on mine and climbing!

Peter

__________________
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!

If you don't get somewhere on this pretty quick, and you have the time and inclination to do so, I would recommend a visit to Continental Imports in Gainesville. One of their principals is a member here with the username of stevebfl. His name is Steve Brotherton, and he really knows his stuff. The shop is a Bosch Authorized Service Center, so they are equipped to handle intricate Diesel related stuff. What I posted before is simply anecdotal and may or may not have a bearing on your engine's problem. It was simply to say that parts can be bad out of the box, and techs don't often think of that. And yes, you described my noise perfectly.

Welcome to Mercedesshop, and be sure to let us know how this thing turns out.

__________________
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

Rick,

Thanks for referring Continental Imports. Although I will keep them in mind, since Gainesville is several hours down the road, you gave me the idea to research to see if Jacksonville has any authorized Bosch Service Centers and sure enough, there are two here: Herndon's Automotive Co., Inc. and Euro Spec, Inc. Since they're both just a few miles from me, I'll check them out first and hope I hit the jackpot. Will let you know the outcome.

Peter,

Appreciate the diagnostics. Reminds me of the troubleshooting charts I used to use when I was an aircraft maintenance officer in the Army. Short, sweet, and concise and it all made a lot of sense.

Thanks to you both for your input. I'm going to get smart on this yet!

Skip

Skip,

Does the car still have the trap oxidizer on it? If so, better head back to the dealer for the recall work.

That could contribute to a poor running condition. Blockage.

__________________
Regards,
Aaron

This is a very common complaint for the 1986-1987 603 diesel engine. They smoke light bluish-gray on startup and idle rough. You take it down the road and a half-mile later everything is fine.

I think its a great problem. It helped me get my car CHEAP! Previous owner thought it was major engine damage.

It doesn't seem to be a problem with glow plugs on my car. I replaced them all with verified good plugs, with nearly the same results. When you preheat with the glow plugs, you might notice that the car starts smoothly with no smoke - then about the time the glow plugs cool down (like two seconds) the smoke starts pouring out and the idle roughens.

Later diesels with the aluminum heads solved this problem by extending the time the glow plugs stay heated after engine startup. On some models they can run up to a minute after the engine starts. No problem on these cars.

The idea of a poorly conducting glow plug relay is worthy of testing - and I have not done that. It should be easy to verify though. You just get a voltage reading at the glow plug when the relay is engaged. The system should be providing a reasonable voltage to the plug, say 11 volts or more. However, I can tell my glow plugs are working - and you can to if you ever try to start the car instantly without waiting for a glow plug preheat. They really, really do not like to start without the glow plugs.

Hopefully there are enough people not reading here that will quickly discard their 1987 300Ds at "destroyed engine" prices!

Ken300D