200,000 miles; well maintained by previous owner. Frequent oil changes, and maintenance done by certified MB mechanic/guru.

Recently the idle became rough. I changed the main fuel filter and the secondary fuel filter. Removed air cleaner cover and continued to run rough. (It is running so rough at an idle that the whole car shakes. Once it gets up to speed it does OK. Power is less than normal. It is smoking-espescially at startup more than normal, and smells like unburnt fuel. It will die at an idle unless you keep your foot on the gas.)


What else should I bee checking?



Thanks for you input in advance

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1982 300CD (Veggie)
1975 240D
1986 190D (lost a bearing)
1982 240D (dead eng.)

How would I check to see if there is a partially clogged injector??? Or is that an area that I should be considering?

My thoughts are to crack the line at the injector of each cylinder and if the idle does not worsen significantly, then there may be a problem with that injector?????

Help please...

__________________
1982 300CD (Veggie)
1975 240D
1986 190D (lost a bearing)
1982 240D (dead eng.)

Are you getting enough fuel at the prefilter? Did you try raising the idle speed? Another thought is the rack damper pin on the back of the IP. Maybe it's too far in.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

I know it has been well maintained but when have the valves been adjusted last? Also a quick check of milli volts on the harness plug might indicate the cylinder with a problem if there is one. If not a cylinder it will show with all voltages being about the same usually. If there is one with low voltage just switch the injector with the next cylinder. Does the problem move? If so get the bad injector checked . If the problem persists on the same cylinder do a compression check on it. Your description could be many things but possibly a cylinder not firing properly is a good place to look. Or thats what I would do first as it is so fast and easy to check. You require a meter with a milli volt function as your glow harness reading will be about 10 milli volts on each glow plug at the harness contacts. With the engine warmed up and running. Edit: re read your post. Sounds like bad injector on rethinking. Too much smoke to be underfuelled.

engine mounts.

OK What is the rack damper pin, and how would I go about adjusting it???

__________________
1982 300CD (Veggie)
1975 240D
1986 190D (lost a bearing)
1982 240D (dead eng.)

There is a bit more of a bubble at the prefilter than usual...

__________________
1982 300CD (Veggie)
1975 240D
1986 190D (lost a bearing)
1982 240D (dead eng.)

That is your problem 99%. I had same issue. Go to parts store get appropriately sized (I think it was 5/8ths) fuel hose and replace the hoses coming from and going to the tank. Takes 10minutes in the parking lot of said store.

I dont know what specific role a ceegar hose plays but using just regular fuel line worked for me.

__________________
http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

barry, could you explain a bit more about how to read the MV's off the glow plugs>? i know there's a big thread about it, but how about the simple things?

attach to the glow wiring harness and to a ground? check for each cylinder?

I've used the infrared temp gun on the exhaust manifold for other engines to check for similar things.

my engine is idling rough but after idling for 10 to 20 seconds it begins to idle rough. like one cylinder isn't firing, then another quits. sounds like they're next to each other in the firing order, because it kind of lopes faster and then slower.

hmmmmm....

switching in a set of injectors tonite hopefully, will report back.

karl

Reading the glow plugs is the simple thing to do. It gets you clear of or involved with the fundemental problem the quickest or most accurate way possible. You either have all cylinders preforming properly or you do not. It is not likely the rack bolt unless the spring packed it in all of a sudden in my opinion from your description. I think it should just grow weaker with age usually. Not a sudden change. But then nothing is impossible. Also the gentleman that mentioned poor fuel lines should be considered. Both from a perspective of him having had simular symptoms in the past and your observance of a larger than normal bubble in the pre filter. I would not even change the injectors out until there was an indication that perhaps one cylinder was reading different than the others by a wide margin. Also the smoking is not an indication of fuel starvation itself but strange things occur that do not make common sense from time to time. Even something like the head gasket failing between cylinders would be indicated. Yes reading the voltage between the harness plug and a ground on the cylinder head would tell you if all was well or not. The beauty of this approach is it's basically easy and might eliminate a lot of head scratching. Very good at elimination or narrowing down problems rather than excess work or expenditure. Too many cases of shotgunning service aproaches in the past. Thats also the primary reason for the emergence of this system as I have read over and over of people with poor idles that are lived with as there was previously no way to cheaply narrow things down.Or required skills that can only be aquired by a working mechanic to be definative.

If there is not enough fuel to get enough compression to reach combustion wouldnt there be more smoking, less burned fuel?

__________________
http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

I was also kind of also wondering if underfuelled might produce smoke. Thought engine would be more likely to not run if that bad though. Also the glow plugs output voltage would all be lower than the normal range. Far less combustion heat. But as I stated since he observed larger than normal bubble in prefilter the lines should not be ignored. I have found on too many occasions what seems logical does not turn out to be the case many times once the problem is located. That is either my lack of experience or luck of the draw perhaps. We at least have the advantage of the answer to these questions being posted by the thread originator pretty soon. A good check also might be to disconnect the return line and make sure fuel is flowing out of it if fuel starvation was suspected. Again the milli volt readings might reflect that quicker and easier. Plus have a look for too many bubbles in the fuel line. Hopefully just a bad injector as he has some spares. Ultimatly when people post their milli volt readings with description of faults they will assist other people in diagnosing probable actual causes and eliminate things. Or they will know themselves what is wrong before posting from their readings. Time will tell. We have never had a diagnostic system for these diesel non computor cars with so much possible potential in my opinion.

When you get air into your fuel line, you get a whiteish/blueish (light) smoke. Replacing the return lines to the tank won't do a thing for you in this instance.

Tell me more about this voltage check of the glow plugs. Are you talking about checking to see if they glow before you start the car? That will give you a rough idle for a while. After the engine heats up, the idle should smooth out. This is a diesel we're dealing with here. Once the glow plugs heat the engine so the compression ignition can start, I don't believe they are a factor. You can remove the battery, the GP relay, wire harness, you name it, and the thing will continue running. They do not "spark" like a gasser engine does.

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1982 300CD Petrol/Black Leather

The glow plugs generate an output voltage when the engine is running. They are acting like thermocouples. The combustion temperature burn is reflected in the output voltage. Usually about 11 milli volts at idle but depends on the individual engine and plugs. Some as low as 6.3 millivolts output per average plug for example. If something is abnormal in any cylinder it will be reflected in the plugs voltage output. We are finding that comparison between plugs is a good indicator of what is going on. So easy to do. Just disconnect the harness and read each voltage separatly at the plug. Right now we have been dealing with the early stages of development by trying to develop it as a superior method to time the injection pumps to the engine. Results look really promising so far.

Interesting. The GP turns heat into electricity?

Cool... "Thermocouples are pairs of dissimilar metal wires joined at least at one end, which generate a net thermoelectric voltage between the the open pair according to the size of the temperature difference between the ends, the relative Seebeck coefficient of the wire pair and the uniformity of the wire-pair relative Seebeck coefficient."

from: http://www.temperatures.com/tcs.html

http://www.electronics-cooling.com/Resources/EC_Articles/JAN97/jan97_01.htm

Well, how about that?

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1982 300CD Petrol/Black Leather