i just had this discussion with someone the other day, my car does the same thing when the temp dips, all cars with modern fuel injection do. the ECU reads the coolant temp and realizes with coolant at a certain temp the fuel in the intake charge will want to fall out of suspension and condense on the cold cyl wall, the colder the temp the worse the problem. this leads to a relative lean AF mix bc some of the fuel is on the cyl walls and not available for combustion, the ECU follows an open loop prewritten program to inject a certain amount of additional fuel to combat this lean condition based on how cold conditions are. it adjusts this based on the ECT until it gets to a point where it assumes the cyl walls are warm and the fuel no longer will want to condense on them. in the end the engine kicks up the RPM to warm the coolant faster so it can enter its normal closed loop function more quickly. ive added a block heather to avoid the whole thing and for $0.05/hr it costs to operate its totally worth it on those really cold nights.
