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 .....

Did you see the note - "The DTC "9" can be displayed up to 12/92 even if no fault exists."

http://www.startekinfo.com/manual/volumes/e2/1_1/m11.jsp

You say it does not smell right so I guess the car is running rich so the would not be a leak in the air system, I would begin to check the engine temp sensor.Code 9 is Lambda sensor in the manual I got. When you already change the lambda sensor that could not be the problem, have you erased the code?

Thanks,

How does the temp sensor affect this? and which sensor will it be? this is an HFM engine by the way....

I appreciate it ...

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1993 300E, 2.8 M104 .....

Yes, not sure what it means though.....


what about the exhaust smell at cold starts?

thanks

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1993 300E, 2.8 M104 .....

Code 9 on pin 8 is all about the O2 sensor & whether or not the heater is drawing the correct amount of current.

O2 sensor codes have nothing to do with cold running fuel mixture.

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What is your manufacturer date? Some cars have known false codes - e.g. 500Es.

I have the 104 engine E320 1994 and the engine temp sensor is on the water pump not on the top but down on the side. The temp sensor is controlling fuel mixture so the mixture is rich when the engine is cold and lean out when the engine get warmer.

Could this stop functioning correctly without triggering a code?

thanks

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1993 300E, 2.8 M104 .....

I guess so if the sensor give the wrong resistance, are the car smelling gas you should check the plugs do they have signs of being wet ( running rich ) or white from fuel starving if there is any sign of rich running , you might need to change the plugs also. If I remember right so have the engine lack of power when you are driving the car. If the plugs are white you must take a look at the fuel pressure and fuel volume, but then you should have hesitations at wot ( wide open throttle ).