That gives me some things to look at.
Checked some old dealership receipts and found that the wiring harness had been replaced due to a short (about 2 years ago). This supposedly cured a previous surging problem. Also because of some other service, the temerature sensor was replaced, and plug wires and spark plugs were replaced last year (cured severe hesitation problems).
Mine is a 93 and I thought the check engine light would come on if the O2 sensor was bad? It doesn't seem like it's very easy to get to, but I will disconnect it and see what happens.
Will check idle switch too. I am guessing here, since some of you have earlier models with air cleaners.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car