Finally gave up trying to solve my 89 300E rough idle (replaced cap, rotor, wires, plugs, OVP, cleaned idle ctrl valve, etc.), and took it to the shop.

Mechanic indicated lamda tower had a vacuum leak at base and was replaced, O2 sensor was replaced, and injector #3 was cleaned and re-installed. Idles much better but still not smooth as glass. Car has 120K so maybe I'm expecting too much.

Here's my questions:

Where is the O2 sensor located (would like to see a shiny new one in there with my own two eyes...)? What is a lamda tower and where is it (thought lamda and o2 sensor were one and the same)?

Thanks for your help.

The o2 sensor is located under the car just behind the tranny bolted into the exhaust pipe.

Lambda is a term that comes into play when speaking of closed loop fuel injection. It is achieved when the O2 sensor is hot and the fuel mixture is close enough to 14.7:1 to allow the computer to constantly monitor and refine the fuel mixture.

What was done to your car was the o2 sensor was replaced then the fuel mixture was adjusted to get optimal smoothness. (I hope)

__________________
Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS

When someone says they have adjusted the Lambda, exactly what did they twist?

The adjustment is a 3 mil screw in the lamda tower

Thanks!! Now all I need to know is where the Lambda tower is:p

LT is on top of the fuel distributor which is under the air cleaner . The tower is often sealed with a plug and it is not advisable to tamper with it unless you have the EQ to read the setting change.Hope this helps