Hello All,
My '94 E320 has acquired a gremlin in the idle. It will rev between 1100 and 1400 rpm in neutral, warm or cold. In gear its closer to 1000 rpm.
Most folks point to the throttle actuator being faulty but I still have cruise control, car not ASR equipped, and I have never thrown up a Check Engine Light. I get the code for "idle control inoperable"

The problem when I began to happen a around summer '09 came on gradually/ would go away as engine warmed up/ was only in neutral. Now I have the above problems.

I have scoured the web and tried as many of the solutions as I could:
Replaced:
Wiring Harness (Jan 09)
O2 Sensor (Summer '10)
New Over Voltage Protection Relay (Fall '11)
Mass Air Flow Sensor (Jan '11)
Intake Air Temp Sensor (Summer '11)
Idle Air Control/Resonance Valve (Late '08)
Cleaned EGR Pipe / Tested Valve (Fall'11)
Installed rebuilt throttle actuator (Summer '11)
Checked:
All the vacuum lines I could find. (Crank case seems to run at a lower pressure then I remember, likes to suck the dip stick in its hole)

Does anyone have any ideas what else could be wrong? I'm so stinking sick of the problem, I have until now been throwing money into best guesses and none have been right.