1987 260e
I searched the previous threads but could not find quite the same set of problems.
Starts up okay, idles around 1000rpm then as it warms up it starts to hunt up and down the rev range with a spread of about 200 - 300rpm's.
If I rev the engine I get black smoke (running rich) if I lean out the mixture it wont start.
I couldn't get what I thought was a correct reading from the 02 sensor (variation up to 1 volt) so I replaced the 02 sensor thinking it was not going into closed loop. no change and still a strange reading on the 02 sensor, I think it is so rich that the sensor cannot compensate. No vacuum leaks that I can find. If I disconnect the electrical connector in front of the fuel dist. the engine will rev up and then return to the previous idle. If I disconnect the temp. sensor there is a change in the running. I get a constsant reading from pin 3 on the diagnostic socket of about 11.34 volts. If I remove the OVP the engine still starts with the same rev variations. Am I right in assuming that its not going into closed loop or ???????
Thanks in advance for the help guys.
Michael

I am having the exact same issue. I hope someone on the forum can help with an answer.

I do not have a260E so my suggestion cannot be too specific but here goes.

It is apparent that your problem is engine temperature related. Your car must have an engine temperature sensor that provides input to your fuel injection computer. On my car (1989 560SL) it is located on top of the engine in the vicinity of the mass air sensor. Replacing that temperature sensor cured very similar symptoms in mine.

There are probably several temperature sensors under your hood, one for your auxiliary fan, one for your temperature gauge and that one. The fuel injection sensor has two wires whereas the others have one and three wires repectively. Remember, we are talking different cars here so you will have to look around or consult whatever maintenance aids you have. I use ALLDATADIY and a maintenance CD.

Good luck Pal and I'm sure we would all be interested in the results of your fix, whatever it is.

Mr White Album !

Thanks for the input. I have been considering what I think they call the fuel injector temperature sensor, which is in the back of the intake manifold area near the firewall.

I only have a book for my 190e which showed this, but the general layout of the engines seems "roughly" simular to the 260e (Minus a few cylinders).

I sometimes miss the days of "simple" engines... like my Cherished 69 AMC Javelin SST, or even my ol' baja bug which I rebuilt 3 times before it was sent off to a mass auto grave. These newer engines with all the sensors and electrical gadgets are stretching my mechanical abilities a bit !!