PeachParts Mercedes-Benz Forum - 87 300E runs great but mpg suddenly bad

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Quote:

Originally Posted by lizem100

...
Just in case, if I buy the Ford O2 sensor do I replace the part in the exhaust or near the seat? In other words does the exhaust part break or the part near the seat(is this just a connector?)

The part that screws into the exaust pipe gets replaced and the connector under the floorwell stays... ...cut the wires closer to the connector on the new unit so the splice is inside the cabin...

also you don't need to drive the car to test it... you can just let it sit and idle until 80 + temp is reached.

Quote:

Originally Posted by lee polowczuk

My drive to work has been reduced from 15 miles one way to 1.5. The heater hardly gets warm.

my average mpg has dropped drastically. I would say from the very low 20's to maybe 15 mpg... however, in a week I am driving very few miles.

I'll take the lower mpg for now. I do have to consider having my wife drive this car to work once a week, however. She has a 30 mile commute which would be better for the car.

That is what happened with my wife. She used to go 30 miles each way to work and drive our C230K Coupe and get 27MPG average. Now she goes less than 1.5 miles and the car gets 20MPG now. But alas I do take it once a week for a run to blow it out so to speak. If not for the heated seats she would never be warm by the time she gets to work. lol

But hey a tank of gas lasts more than a week now.:D

Voltage still 11.35 no fluctuation after ccoming home- 7 miles. I guess I will drive for a week or so and retest to see if proper temps help things.
A26 says the reading does not make sense re the O2 sensor. Will see how mpg changes. Worst dase scenario I go to the Jan tech session and ask the MB shopforeman.

Final Result to this saga

I went to the tech session yesterday thinking my O2 sensor was bad. Lead tech at dealership hooked up their analyzer to the X11 connector. It read 2%(I am not sure units) and did not vary. He said it was too rich and needed more lambda. He took a 3mm allen and adjusted (near the air intake) the mixture more lean. The final result was 4.5 varying up to 5.5. Thus the sensor is fine. (I let a shade tree style indie touch the richness several years ago after fixing a water pump.) Perhaps the broken thermostat and the excess richness caused the apparent sudden drop-will need to monitor mpg and report.
For A264172's benefit I checked my X11 with my multimeter. I got 6.75v up to 7.5v. So it varies now.
Re O2 sensors- both Bosch and NTK have toll free number to call for tech info. The 13953 sensor used at one time one the Ford Mustang(Parts people now rec 13942 shorter cord for the Mustang) now rec on E 150 econoline can be spliced in though it has a 6 ohm heater instead of 4.5 ohm. Not sure if the ohm diff matters. NTK had a $29 one with a short cord(theoretically bad as solder will be outside cabin) and correct 4.5 ohms.
Many Thanks to all who helped.

Thanks for the follow up.
That's something I haddn't considered; running so far out of adjustment range that there is no visable fluxuation.
Glad to here it's runing good and not fouling your cat anymore.
Congradulations.