Note that when this happens, the O2 will foul in as little as 10 minutes. When you install the new or cleaned O2, does the car run ok for a little while, then go back to the "status quo"?

Although not on this motor I went through a nearly indentical problem on my 16V(also "KE")..turned out it was the ecu. However in the process, I messed up three O2 sensors....I was able to recover the last one by cleaning it on the bench and re-using it....what I did try was to disconnect the eha, then re-adjust the mixture, and ran the car tuned "manually". Although not perfect it allowed me to run semi normally over 2000 rpms.

Bottom line...we tried another ecu from a different car..and it solved the problem(after we retuned the air fuel mix..leaning it way back down to the correct readings with everything reconnected)...Actually we tried an ecu from a 2.6 W201, and guess what..the car runs fine with that too...strange.

MDE3
Thanks for joining the fray.

interesting input. As to the 02 sensor, the frustrating thing is nothing I have changed, swapped, replaced etc. has made any difference at all. That's why I am beginning to think ecu. I do want to check continuity on the 02 sensor green wire. The trouble with changing so many parts and testing is you're never sure if you have't pulled a wire out or broken some internal connection. I have no base line to judge anything by. Like you I have tuned the car without eha and it runs okay (hard to start) but that's not how I want to run it. I wish I could lay my hands on an ecu to just plug in and see if anything changes.

Michael

You can check the O2 with a DVM..basically if your car is like the 201's the connectors for the O2 are under the mat on the front passenger side. Just hook into the connection in parrellel using a small shunt inserted into one of the black connectors while leaving it connected (not the white ones as they are for the heater circuit) to which you attach the positive alligator clip...and then ground the black to frame(seat bolt or similar). With the motor warmed up, and held at about 2500 rpm's you should see the voltage fluctuate above and below .5V (Dvm set for 2v). If it is not functional, you will see a reading that stays below .5V.

If the condition you are seeing is similar to what I had, then your O2 may no longer be functional. They blind pretty quickly in a very rich air/fuel condition. At least mine ran well for a little while...so I knew the O2 was contributing to the problem...but the real cause was the failed ECU..creating the rich condition that was blinding the O2's.

We also had similar readings to yours at pin 3 when checking voltage with the eha disconnected and ignition on but motor not running before swapping ecu's...With the new ecu we got 11.9V, and then when running around 6.5 - 7 V once the air fuel mix was leaned back down (from memory..it was three years ago now). Now this was in a 16V, but I wager they are pretty similar readings for your car....dependant on the KE function.

Something new to report,
I removed the airflow sensor pot. and gently wiped the 2 tracks clean. Now I'm not sure that did anything, but I just reinstalled it without calibrating it and the rpms went up considerably, about 1500rpm idle with motor warm. Also the duty cycle seemed more active.
Tomorrow I will set the airflow pot. buy reading the voltage across pins
1 & 2, value I believe is .75v +/- .10v. May not mean anything but a change never the less.
I guess the airfow sensor is a kinda throttle position sensor.
I'll post the results after fine tuning.

Michael

Well I replaced the airflow sensor pot. and yesterday I set it .65v idle with motor warmed up.
The fact that there were changes in the running of the motor from removal to replacement leads me to believe that the sensor is working, so I guess I'm back to square one. I need to try a replacement ecu.
I'll check ebay etc. the Bosch number is 0280 800 212 and the MB number is 005 545 8032. If anyone out there has one for sale please let me know.

Thanks for all those who helped me.
Michael

Michael, I have an ECU from a 1988 300E I'm parting out (buried down somewhere in the part forum) $25 delivered to your door in the USA48.

Let me know.

Update. '87 260E
For all those that helped with input into my problem I thank you. It turned out to be a bad fuel injection ECU. Plugged another one in, reset the duty cycle and now I can run it all day with no smoke.
Now, here's something to ponder.
I have read so many posts with regards to hard starting hot and cold but no one seems to know the answer. Now that the car runs well and I can use it I now notice that I have the hard start problem.
?????????
Michael

there is a relay near the injection ecu, i think it has 2 circuit breakers on it, this controls the idle and start, try replacing it. if its faulty a new one will give u lovely pickup from idle and reduce ur fuel consumption.

__________________
Jay,
-----------------
-1995 Blue W202 C36 AMG (M) SOLD ;(
-1995 Black W140 S500 (Lady)
-1992 Black W124 E300 (Dima) (Ex-Mosselman
Twin turbo Kit).
-1988 Black W124 300 E 4-Matic.(Nadeen)
-1983 Brown W126 500SEL.(Old Lady)(Sold)
-1981 Gold W123 280CE.(Dareen)(Sold)
http://www.youtube.com/user/jayrasheed

Thanks JayRash,
I think you mean the OVP relay. Mines appears good, from my reading of previous posts it powers part of the ABS circuit. Tell tail sign of a problem with OVP is ABS light on.
My start problem feels like the gas drains back to the tank and I have to wait for it to pump back up to the engine.
I will take another look at the OVP and thanks again for your input.
Michael