When its cold out the car doesnt want to idle. We have to keep revving at stops. on 2001 BMW 330i

I think its taking on air but from where and how much does it cost to fix?

Asked by for the 2001 BMW 330i
Is the check engine light on? Does it start and run normal until it's warmed up?
Check engine light is on. The car runs fine when its warm OUTSIDE!
Have the CHECK ENGINE light DIAGNOSED. Don't put parts on because of a code. Have the cause of the code determined. Possibly faulty coolant temp sensor or problem in that CIRCUIT (wiring , connection(s) or low coolant) , or several other possibilities.Parts places SELL PARTS they don't diagnose---just my opinion...Good luck.
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check for codes