My 1992 300E with 50,000 miles has been running fine after a installing new O2 sensor. Now on cold start engine stumbles and almost dies until warmed up a bit. Sometimes engine nearly stalls when I accelerate from a stop before engine is at operating temp. Checked the idle air control and zero resistance(assume IAC should have some resistance) and voltage to the IAC was 2.4v when engine was at operating temperature. OVR was recently replaced as well as both engine temperature sensors. Any thoughts?