Strange Idle Behaviour

[kwbimmer]

1995 525i, auto - 220K kms

During a cold engine start my 525 will idle at 600 rpm.
As the engine comes up to operating temperature range, it will idle normally at the 900 rpm range.
If the engine has been running for an extended period (1/2 hour or so) the idle will fluctuate, consistently increasing to 1,200, then dropping to 900.

It appear as though there is a reverse of the choke function occurring. This makes cold weather starts very difficult. It got to -16 C yesterday in Waterloo (Brrr) and It took 20 mins and a continous boost from my 2nd vehicle to get her going.

Any suggestions?

[BillionPa]

possible temp sensor failure?

air intake temp sensor?

[kwbimmer]

possible temp sensor failure?

air intake temp sensor?

Would this come up with a code on a scan?