I recently took my 1993 400e to american service center in arlington because it stalled and would not start properly. They diagnosed it as worn engine wiring harness and replaced that, as well as the crank shaft positioner. Since I got my car back I have been getting TERRIBLE gas mileage. 10 MPG if I am lucky!!!!! I used to get at least 20 before bringing it in, and I know those are capable of pulling mid 20's.

Does anyone know of why this change might have occured? I called back and the guy claimed that both parts have nothing to do with anything that could affect the mileage so drastically. He told me that it would either smell like gas, or run terribly, but the funny thing is it does neither. Is there something they might have knocked out of place or altered while working on these parts? Please let me know if anyone has heard of this or has any suggestions. Thanks.
P.S. I love this site.

The upper wiring harness allows communication to the fuel injectors, Mass Air Sensor, coolant temperature, intake air temperature camshaft position .. etc. Depending on the values communicated to the Engine Control Module, your engine will adapt to various conditions.

I would have someone read the engine codes. Fault codes could be causing your poor performance. I.E. When the ignition control unit recognizes a specific type of failure, it sends to switch off all affected fuel injectors. Reading the fault codes could also help verify all connections on the new wiring harness are functioning properly.

I have a 93 400e also and I never get a "check engine light" even with various fault codes.

I'm sure there are others here on the forum that can further elaborate.

__________________
Russell McMahon
Tulsa, OK
2001 CLK 320
1992 400se
1993 400e
2000 320ML

hmm, very interesting. Unfortunately I have to take the car back to school. Do you think a regular garage or mechanic would be able to troubleshoot this? Do you think it is bad for me to continue driving it? I am in between a rock and a hard spot.

If this is indeed a control issue, a regular garage will not have a clue. You're better off going to your indie MB shop.

Taking into consideration your circumstance, I might disconnect the negative connection to the battery for a short time which in turn will clear fault codes. While the battery is disconnected, I would use the time to visually check all the connection on the upper wiring harness. (Just remove the air filter housing and the front cover – you don’t need to remove any of the engine side covers to review the upper wiring connections.)

Reconnect the negative battery terminal in the trunk (battery). Take a long screwdriver and place it on you ear as you listen to each fuel injector. Kind of like a stethoscope. You should hear a clicking nose coming from each injector. If no clicking nose, check the wire connection to the injector.

Drive the car for a few days as the Control Unit adapts to the new values. If new codes are generated, the shop will know the code were generated after the wiring harness replacement.

I the problem persists, have the codes check at a MB equipped shop. It will have to be a MB shop since the plug for the code reader is an OBDI Mercedes specific connector.

There are numerous other technical steps you could take to look for problems, but this might be good 1st step.

You didn't make mention the car's performance. I assume without the gas milage problem, it's okay?

Later you might want to review the O2 sensor, rotor caps, rotors, plugs, air filter, (tune up items)

Good luck!

__________________
Russell McMahon
Tulsa, OK
2001 CLK 320
1992 400se
1993 400e
2000 320ML