Hello Everyone! I noticed recently that heat and a little cold comes out of the air vents even if the AC button switch is OFF. I also noticed my gas consumption go up, from 24mpg to 21mpg. Idling is around 700rpm while in Park, then goes down to 400-500 when in drive. It wasn't like this months ago. Please HELP! Thank you.

 

V6 or 4 cylinder? Automatic or manual climate control system?

 

Manual climate control system

 

Something called the Intake Air Control (IAC) valve sets the idle. The electric valve bypassed engine intake air around the throttle plate based on inputs for the engine computer. Try cleaning the valve. The internet has video's etc on this. If 4 cylinder the engine model is 5S-FE.

The manual climate system has a rotating **** the moves a valve in the coolant line going to the heater core. Have someone rotate the valve while you watch the valve arm for movement. The valve is located on a hose that goes into the firewall on the drivers side. A push pull cable moves the valve arm.

The climate system air intake chamber under the dash has something called a blend door. This door door mixes the air outputs from the heater core and AC evaporator. Make sure t the door is not stuck in the position that only allows hot air from the heater core.

The AC compressor is either on or off. The button turns the controls for the compressor on which the cycles the compressor on/off to maintain the chosen cabin temp. The button doesn't activate any blend doors, etc.

If decreased MPG check for vacuum hose and engine air intake hose leaks, spark plugs, etc.