I've been dealing with code 9 on pin 8 for quite a while....the mixture just does not smell right especially at cold starts....

so, from my understanding, code 9 means that the computer reached its limits on adjustment. it cannot adjust mixture anymore due to external factors such as a vacuum leak, or a fuel system problem....

So I checked all vacuum lines (maybe for the tenth time already)...everything is nice and holding vacuum....

I have two functioning MAF sensors...car exhibits the same problem regardless of which sensor is installed.

I sealed off the vacuum line going into the purge valve since the valve appears to be faulty.....

I just changed the fuel pressure regulator with a brand new Bosch one....

this is the second O2 sensor that I install in this car in the last six months....both Bosch (universal 4 wires with the secure connection thingy) .....

So what the **** is the problem? Bad computer? Bad injectors? Bad engine???

What to do next other than taking it to a Mercedes shop? i reached the limits of my patience on this one.....

I clear the code, and it keeps on coming back after a while....

any advice is highly appreciated....

Thanks

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1993 300E, 2.8 M104 .....