How many miles does the car have on it? What is the service history of the transmission?

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1987 300TD 309, xxx 2.8.2014 10,000 mile OCI


Be careful of the toes you step on today, as they may be connected to the ass you have to kiss tomorrow. anonymous

“Be who you are and say what you feel, because those who mind don’t matter, and those who matter won’t mind.” Dr. Seuss

I think Tim is on to something. If you have checked for leaks, and are sure there are none, this could be one possibility. If the return fuel is being diverted to the "empty" WVO tank, that may account for your poor mileage. It would be nice if you could find out how much fuel is in the "empty" WVO tank. It may be the answer you are looking for. Good luck

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96 E300d

Ok. On my last "tank," which included 10 gal of wvo and 20 of diesel, I was able to drive a total of just under 700 miles giving me 23.3mpg. Assuming there was more fuel in the wvo tank than I thought, this calculation would be falsely high. An other possibility I'm considering is that in removing my broken front anti-noise capsule and tying up what is left of the rear one, the reduced aerodynamics could have something to do with the drop in fuel efficiency. I've sent inquiries to junkyard databases so far with no luck. Do any of you drive around without the anti-noise capsule? It's name appears to indicate that aerodynamics is not what it's for but it doesn't look like it would hurt.

I seriously doubt the aerodynamic drag of not having the antinoise pannels in place would make any real noticeable difference. My 1996 E300D was missing two of the three pannels when I got it ..... I purchased new ones a couple of months later ..... but didn't notice a change in fuel mileage.

David Roseman
Long Beach, Ca

Have you checked the operation of the three intake runner/manifold flaps? In the 1995 & 1996 E300D's there are no micro switches on the flaps so there is no feedback loop for the engine computer to know if they are functioning correctly or not. If the main intake flap (by the air cleaner assembly) is malfunctioning the engine would be starved for oxygen ... or run rich. I think it is also possible that malfunctions of the other two flaps in the intake manifold system could effect air flow efficency, but probably to a lesser extent. I don't know how running on alternative fuels changes the exhaust gas composition .... but its probably possible that EGR system and the three flaps could be gunked up with exhaust deposits from the alternative fuels that the engineers never designed the motor to deal with. I'd check the operation of the EGR and three intake flaps to make sure they are running properly. There is also a small sensor connected by a vacuum type hose from the intake manifold that measures pressure in the intake manifold system ...... I would check to make sure that the hose hasn't disconnected or is cracked thus providing the engine computer with wrong information on intake manifold pressure. Good Luck ..... minor problems are sometimes difficult to figure out.

David Roseman
Long Beach, Ca

245K miles. I'm not sure of transmission service history as my records show nothing of the sort. I know the previous owner had no transmission work done but I'm not sure beyond that. I am at least the third owner.

The sensor that connects to the intake manifold is not present on my model. Otherwise, I'm glad you brought up the intake flaps, David, as that was one of the next places I was about to consider looking. In an earlier thread, pberku suggested that I pull on the accelerator cable to increase the engine speed past 1500 rpms. With a warm engine, this should cause the bar that connects from the throttle linkage to the first intake flap to move on its own. At the time, when I performed this test, the flap appeared to function fine. I tried it again, tonight, this time, however, nothing happened. I had just driven about ten miles, so the engine was warm for a while. Between now and then, I had removed the intake manifold several times, so it's possible that I may have forgotten to reconnect something. The question now is what. Also, last month I thoroughly cleaned the intake manifold and crossover pipe with dawn so there shouldn't be any gunk blocking the flaps. It looks like I will soon be removing the manifold again so I will check. By the way, how would I test the other flaps?

Although the engines are essentially the same between the '95 you own and the '96 & '97 models I own .... sometimes I forget that the controls between them are different. On my cars I removed the flaps from the crossover pipe and the intake manifold (a couple of screws hold them in) and then scrubbed them clean to a shine with an old toothbrush and degreaser. While I had them out I applied vacuum with a hand vacuum pump to the actuator and watched the movement of the flap. On three of the flaps (two cars) the flaps moved fairly quick into position and then when I released the vacuum the flaps snapped back into place quickly and made a slap sound as the flap struck the stop. I had one flap, even after cleaning, that was "lazy" in its movement, moving slowly into position under vacuum and slowly back to the stop when the vacuum was released. I just replaced that one flap and my check engine light problem was cured. Since you will have everything apart, for good measure I would also replace the vacuum control hoses if they look worn or cracked. When everything is back together and the engine is running you should be able to observe, and hear, the flaps move as you pull on the accelerator ..... I forget exactly, but one flap moves a little over 1,000 rpm (one in the intake manifold I believe) and the other one (in the crossover pipe) around 3,000 rpm .... and a of course they move back as the rpms decrease .... again movement in both directions should be swift. Good luck.

David Roseman
Long Beach, Ca

I was able to check all three flaps having only to remove the crossover pipe. The manifold and crossover flaps as well as the EGR valve look to be working fine, but I didn't check the exact rpms when they moved. After cleaning the flap and pipe between the air filter and crossover pipe, it remains unresponsive. I pulled the vacuum hose to make sure the flap itself wasn't broken and as I suspected, there was no suction at all in that hose when I pulled on the accelerator cable. Could this have anything to do with a bad coolant sensor or the associated wiring? My thinking is that if it were, then the other flaps wouldn't operate either, but my knowledge isn't very extensive. I'm currently looking for loose or broken hose connections, and so far have found none.

If you would like another pair of equally un-techinal eyes to take a look at your plumbing sometime PM me. While not as familar with your engine as some others I have a reasonable understanding how it differs as compared to my 99.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

On both my '96 & '97 models the EGR and intake flap are controlled by electro-vacuum valves (two of them) located adjacent to and below the air filter box. It is possible that either the vacuum lines have come loose, a vacuum line is leaking, or that one of the valves is malfunctioning. The two valves are identical and they have three ports each. These American made valves cost about $120 each and rarely fail. I would first check to see that each valve is supplied with vacuum to the "VAC" port. If not then you have some other open vacuum line that will have to be traced. Since the other two flaps work and the brakes work its probably not a problem with your vacuum pump. If you find that vacuum is supplied to the two valves, yet no vacuum is present at the "OUT" port regardless of engine speed then its either the valve or the electronic controls. There is a test proceedure outlined in the MBZ service manual .... but one easy way to check is to just swap the vacuum hoses attached to the "OUT" ports of the two valves .... if your intake flap suddenly works and the EGR doesn't then its the valve .... if the problem is unchanged regardless of "OUT" port connection then its an electronic control problem, which will either result in a lot of research with the MBZ service manual or a trip to the mechanic. Of course what I just described applies to the '96 & '97 models ..... I'm guessing the '95 is similar but perhaps not exactly idendical.

David Roseman
Long Beach, Ca

Both valves are supplied with vacuum. After swapping hoses on the EGR valve and intake flap, the functionality of the two did, in fact, switch. Just to be sure if it was the electro-vacuum valve, I swapped electrical plugs as well and found that the valve that supplies vacuum to the intake flap actually did begin to work. If it is an electrical issue, where should I begin looking? I've already cleaned the plug and pins. Is there a fuse on the circuit I should be looking for? I should also mention that last night, with the car running warm, the EGR valve wasn't working at all. Now it works fine, but I'm still getting nothing out of the intake flap using the intended wiring and hose configuration. The wiring doesn't look to be degrading but I will check it more thoroughly.

Wow .... I'm not sure. From your description is sounds like the problem is somewhat intermittant ...... so I doubt it is a fuse. Then again the modern fuse box on the W210 models virtually eliminates the fuse problems of eariler models .... so if your 1995 has the old style fuse box with round style fuses then perhaps checking the fuses and cleaning them might be worth a try. When you swap the two valves does the intake flap work all the time? If it does then I would consider taking a chance and purchasing a new valve because electronic issues are difficult to track down and it is possible that the valve is intermittantly bad either on the vacuum side or the electronic side. If swapping the valves doesn't correct the problem for the intake flap operation then the problem is probably electronic. The problem could either be in the control wire(s) from the ECU to the valve, or it could be the ECU itself, or it could be a bad sensor or wiring connecting one of the sensors to the ECU. I don't know what sensors drive the movement of the intake flap via the ECU. Trouble shooting such a problem requires a manual and wiring diagram to do it right. Good luck.

David Roseman
Long Beach, Ca

This past Friday I had a mechanic (thanks for the recommendation Terry) run a diagnostic on the computer system. He didn't provide any concrete conclusions, but recommended that I replace the coolant sensor and voltage relay. He further stated that with a bad voltage relay, the air/fuel mixture becomes very rich, which would cause my poor fuel economy. The problem is that I don't know what he means by voltage relay. I called him today and, I guess being to busy to talk, he said to ask at the dealership and they will know immediately. Is it the ovp relay he's referring to? I tested the ovp as per the instructions at Help!! Need OVP plug schematic!, post #58, and got supply voltage to pins 30a, 87E, and 87L just as it describes. Could he have meant the EGR relay? My EGR valve hasn't worked since 4 or 5 days ago. Would the EGR relay control or have any effect on the intake flap? Unfortunately, I don't know which coolant sensor to check/replace either? I was told that it is not the two-pinned blue one to the left of the fuel filter, and I recently replaced the 4 pin sensor beneath the intake manifold with no improvement. Are there any others? I've heard there are three coolant sensors, but I'm not sure if my car is set up the same. Since a coolant sensor may play a significant role here, I figured I'd mention that I recently noticed that my auxiliary fans don't work either. I tried jumping the two pin coolant sensor, but that did nothing. Sorry for the cluttered information. I don't mean to try to have all my cars issues solved in this thread, but I just thought that knowing this could in some way help get to the bottom of this.

Did you got to to Medi? If so, he was probably refering to the OVP relay I'm guessing.

Can't remember, does your AC work? If not that may be why the AUX fans dont come on as they are there mainly to cool things n stop and go traffic when there is little or no airflow.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Yep. AC blows, but not cold. The thing is, I thought that if I jumped the two pins on the blue coolant sensor, the fans would run constantly, yet they do not. I suppose it could be something else. Anyway, I'm working on an other coolant sensor, so if that doesn't work, I'll check the ovp wiring next. Does anyone know where to get a new plug (126 540 30 81) for the 4 pin coolant sensor (008 542 32 17, listed as water temp. sensor)? If not, is it possible to break it open in a way that it is still usable? The wiring is degrading all the way to the plug.