There are three temperature sensors on the car. One is only for the guage in the dash. The coolant temp. sensor allows the engine to run right at any engine temp. The air charge temp. sensor corrects the fuel mixture for the ambient air temp.
The MAF is composed of BOTH the air flow sensor and the air temp. sensor. If the air flow sensor is dirty it will cause a lean condition which may seem worse in a cold engine but will affect performance at any temp.
If the heating element in one or more of the O2 sensors is bad it will severely lengthen the time to reach closed loop operation.
Also beware of vacuum leaks and leaking EGR systems.
If the engine itself is slow to heat up (read - no heat from vent), that would be the thermostat.
