Air flow meter

Air sensor for 99 Protege 1.6L, might be applicable to your car as well.

There are two screws on top of the sensor, which should be located past the filter on the air intake. Remove the screws carfeully and pull the sensor out. If you look through the sensor, there should be a tiny element, use throttle body cleaner to blast any deposits off the element, and clean other parts of the sensor while your at it. Just be careful and don't physically contact the element.

The cars computer detects the amount of energy required to heat that element up to a certain temperature, and relates that power requirement to the amount of air flowing by (air temperature and pressure is also measured by the computer). When the element gets dirty, it becomes insulated and the calculations are affected, which will cause the car to hesitate on acceleration. Fuel economy is also affected.

You might hear from people that this part can't be cleaned, I've been doing it for the last 4 years and it is the best 'tune up' you can do for the car, it will run like new!