The car is a well maintained 1995 E320S with 171k. The idle in drive (air on or off) always had the needle on the tach resting on top of the five, now for some reason the needle is just under the ten mark on the tach(in drive) . It has no rhyme or reason. This is what I have tried so far, airflow sensor, idle actuator and the temp switch for the EFI computer. Any ideas? When I come to a stop sometimes it drops to its normal mark then sometimes it just jumps up, no bouncing around or anything, it just jumps up. Your thoughts are appreciated.

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Mike

90 300D 511k
95 C280 133k
14 BMW 528i