I have a 1988 190E 2.3L. (Ca emissions). The head was rebuilt by a "mercedes specialist". I found that none of the updates on valve train bolts etc. were performed as required by a TSB I read, nore timing guides replaced.
It lasted 14 months. guide broke, jumped time, bent valves. That was harsh.
I bought a used 2.3L from a 1987 (federal emissions) that was T-boned.
I heard it run, and the seller pulled it. When I went to pick it up, the carcass had been hauled off, and he had cut the harness. I had to change all the components to match the existing harness / computer? . I believe pin 15 is 02 mil control if federal, and battery 12V (+) from OVP relay if Ca. I now get code 5, and have one harness wire (Red, White, Black) left over. Schem. shows that color in 02S circuit. It also gets up to 105C prior to fan engaging which I guess is normal. Also, there was some major blowby, but it went away. Maybe a ring stuck and reseated? And it cranks hard like there's no ignition on crank, but when fires, it runs great and more power than the last engine. Smokes the tires. OVP is good, cold start valve is good, May have sticky advance on dist. It seems that that connector under Passenger floorboard for 02S was not part of the harness components. I checked the connection and seems ok. Then, the next drive cycle, the MIL did not iluminate. It even ran cooler, (may be thermostat.) I went through emissions test station, and when he was done, I passed, but the MIL was illuminated. I got code 5 and reset it. It came back on. I also noticed the auxilary air device is not installed on this engine. I don't know if I should hook it up, lacking some shaped hoses. I am not a Mercedes Tech, but I might be by the end of this project.
*I called the dealer, there is no reset code for the radio. I have to take it in and have them use a special tool? My Question is, What is most likely going on?