No High Idle When Cold?

[nitroracer]

New owner checking in, trying to fix some of the deferred maintenance problems on my new 87' 325is. I have been reading up on idle issues with M20s and I have a problem that isn't the normal high idle or rolling idle issues - my car has no high idle on a cold start. The last few days have been in the 30°s and my car would start and try to run in the 800-1000rpm range which seems a bit low for such cold temperatures. It doesn't die, but just off idle the rpm drops before the car gets up to temperature. Other than that it runs great. Occasionally I will get a check engine light, but only after the car has already warmed up and not every time I go for a drive. I have the earlier 153 DME so no useful codes to read. The throttle position sensor checks out ok at the open and closed positions, and my idle control valve is clean and seems to be running as it should. I am leaning towards a bad coolant temperature sensor giving a false, higher temperature reading that may be causing the problem. Any other ideas for items to check and test?

[SmokeE30]

Vacuum leaks would be another thing to check for but coolant temp sensors are suspect too

[nitroracer]

I'll check for vacuum leaks after the holiday is over. I can see some lines that look to have been replaced by the previous owner, but that doesn't mean it was done correctly.