'92 190E 2.6 runs great, WHY?

Hmmm... I am wondering what you are asking of us... your car ran great after you did routine maintenanced... yet you are sort of asking how to put it back to crappy running condition?

I would say the cleaning the battery cable and post probably did the most trick... second is the O2 sensor.

No...there is now, NO "stuck in gear feeling, of pulling a trailer while the catalytic converter warms up. This started two days ago. You can now get in the car, after overnight, start it, and drive it ....with immediate gear changes............no lugging.

It is summertime now... it is hot enough or warm enough that the emission control system have estimated that you don't need those extended gear shifting interval.

I forgot to ask you how many wires you have on that O2 sensor... If you have three or four, then that is a heated O2 sensor... If I am correct, then your heater on that old O2 sensor is dead.

When winter come, that extended shifting will come back.

I'd say that you should count your blessings and put a little extra in the offering plate this Sunday.

I just had my wife's car serviced (120K) and part of the exhaust system replaced. It now runs like new - engine is smooth and has great acceleration. I'm sure not going to question or complain about it! I'm just hoping it doesn't need more work for a while.

:-)