This can be caused by a number of things, the most likely being a failure in the oxygen sensor or it's wiring, like a broken or corroded harness.
P1131 = Insufficient switching O2 Bank 1 Sensor 1 Sensor/lean. Could be a B1 S1 O2 sensor going bad.
were is the iac locate on a 1999 mercury mystique
The thread on cap on your engine coolant reservoir is the pressure cap / radiator cap on a 1999 Mercury Mystique
Yes , the ELECTRIC fuel pump is inside the gas tank on a 1999 Mercury Mystique
According to the 1999 Mercury Mystique Owner Guide : ( 58.5 liters / 15.4 U.S. gallons )
According to the 1999 Mercury Mystique Owner Guide : ( 58.5 liters / 15.4 U.S. gallons )
The 1999 Mercury Mystique OBD 2 port is under driver side dash next to hood release
According to the 1999 Mercury Mystique Owner Guide : ( 5W-30 ) certified for gasoline engines ( 2.0 and 2.5 liter )
IN the Middle!¬
The thermostat for a 1999 Mercury Mystique is inside of the top water inlet. Remove the top radiator hose from the engine, and then inlet can be removed to get to the thermostat.
In the drivers footwell behind the kick panel ( there is an access hole in the panel ) according to the 1999 Mercury Mystique Owner Guide
Personally, I get about 23 - 25 mpg. on my 1999 mercury mystique. I haven't counted high way mileage yet because I don't get on the highway alot.