87 300E runs rough at idle & low speeds, lamda sensor?

so my old 87 300E seems to be running a bit rought these days when idling and at low rpms. Run she runs, she runs good, but not when idling. Could this be the lamda sensor? Speaking of lamda, could an adjustment be made that would fix this problem. Much thanks in advance.

[Mick J]

Could be vacuum leaks which may also cause rough or late shifting or OVP relay which would bring on the ABS light also. Check these before the Lambda.

I've checked the vacumn hoses, now I need to located the O2 sensor. Any ideas? Thanks. I'm guessing under the air cleaner assembly?

[J.HIDALGO]

The wires run inside the vehicle under the front passenger's seat.
Let us know what happen!