i'm too rich! what is an O2 sensor? 280 te1985

[w123jab]

the saga of the 280 continues, today i took it out for it's first drive in two years of idleness. at first it was very bumpy, both driving and stopping, the latter i take to be rust on the discs.

the gearchange was slow and sudden but i hope this will smooth out with use. however, there will be no further use until i sort out this rich running problem.

black soot coming out of the exhaust, and plugs fouled up so much that the car now dies at idle. this latter problem caused me a great deal of stress trying to get the car out of a supermarket car park safely. the car being an automatic doesn't like to be revved when changing gear! but dies at idle. so i was left with a delicatte balancing act of gentle aggression!

let's just say that the sight of a huge old 280te wheel squealing out of a parking space was one that managed to frrighten half the children in the south of england!

someone said this rich running might be due to an oxygen sensor, i take it to mean i dead sensor! where is it and how do i test for it?

as always, i am in your hands and eternally grateful for all helpful and witty replies

regards

justin

[sixto]

Read this - http://www.peachparts.com/Wikka/EngineControls though not everything will apply to your car.

The oxygen sensor is along the exhaust pipe/s. Start in the engine bay and work down the line looking for something that looks like the top half of a spark plug with 2 or 3 wires stemming from it.

Sixto
95 S420
87 300SDL

[w123jab]

thanks but would this be responsible, if broken, for the constant rich running, and if so, how do i test it to check it?

also, since the car has been standing for at least two years, is it possible that the sensor is 'dormant'? in other words, is it possible to fix the sensor if it isn't working. i mean if it has working parts inside it, then perhaps a gentle tap would help, or a clean with something etc etc

thanks

jb

[MTI]

The sensor is basically a passive voltage sending device, so I doubt "tapping" it will fix it, although if it's just a bad wire or harness connection, you could certainly check that out by checking the connection under the passenger seat carpet, or wherever the sensor wires enter the car from underneath. The sensor is inopperative until it reaches operating temp, so it has virtually no effect on starting the car, but will cause the fuel computer to pass too much fuel to the cylinders if not working. That "over rich" mixture will wet the plugs, give you lousy MPG, and sluggish acceleration.

[stevebfl]

Before you get too wrapped up in this quest, be sure you do have an O2 sensor. A 280TE isn't likely to have an O2 sensor.

[84300DT]

justin i doubt 02 sensors were even made in 1985. altho in today's cars it would make you run rich if one was out. suggest you do following - change the oil , and then take it on the M1 and blow the heck out of it. that should burn the carbon off the plugs and use up some old gas (umm i mean petrol

[MTI]

My 1985 W201 has an O2 (lambda) sensor. It's an integral part of the Bosch CIS fuel injection system, especially if emissions was an issue and if the car is equiped with a catalytic convertor.

[stevebfl]

MB has put O2 sensors on all US gas models since 1980. That did include one or two years on the M110 engine, but there never was a US 280TE and Europe was much later to using feedback control.