1996 C280 Occasional Idle Problem (surge)

[Mino Erhan]

Hi there,
Long time no problems!!!

The idle speed (on occasion) starts to go up and down from 600 to about 1100rpm.
This NOT A/C compressor related.
It suddenty goes up/down, up/down maybe 10 times in a row, in a rapid frequency. Then its OK.
NO MIL light. NO codes. However, as I was checking the codes, I noticed a
P0101 being set sometime ago. I cleared it.
Luckly it did the same thing about an hour later, when I checked the code, there was none set.
I am not sure the code is related to the problem. The code points to a MAF sensor, but I am not sure its the problem.
Car has 137K. Could it be a drifting O2 sensor?

Any ideas?
Any help is much appreciated.

[suginami]

Vacum leak, bad mass air meter, or bad throttle actuator.