oxygen sensor

I have a 1989 560 SEL. The car is running really rough. It really shows up if car is stopped for a red light or traffic. I'm afraid she'll leave me in
traffic. It says in the owners manual that if the car runs rough (shaking) at lights or low speed (TRAFFIC FOR ME) it's the oxygen sensor. I also spoke with a mechanic and said there might be an air leak somewhere. How would I go about checking for an air leak? WD-40? And where is the oxygen sensor locates ( I know it's in the pipe, but where?)
TIA,
Bill
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First of all, you need to check what is wrong with the engine. Pull the spark plugs out and see if you got abnormal colors on the white insulator. If you got black spark plugs, then you are burning oil.
How many miles are on the car?
Check your transmission fluid level... is it low?
How about your engine oil level?
What does your exhaust smell like? Raw gas? Oil? Transmission oil (acrid smell)?
O2 is located in front of the cat converter...Usually in the smaller cat converter closer to engine. You will see one wire.
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