It seems that your thermostat is not opening.
assume you have checked the bulb ....... many auto aircon systems shutdown on loss of refrigerant gases to protect the compressor. Been gassed recently?
under your air filter
lets warm air in when it reaches a certain temperature.
The intake air temperature sensor is built into the MAF sensor on a 1991 Nissan pickup. It is between the air box and the throttle body.
yes
no
no
sounds like a temperature sensor problem
in the gas tank, it is part of the fuel level sensor
temperature sensor.
below the raditor hose that's connected to the thermostat.
no