MAP sensors fail by getting clogged, contaminated, or damaged. Sometimes, engine heat “overcooks” the MAP sensor's electronics or cracks vacuum lines. If the MAP sensor goes bad, the ECM can’t accurately calculate engine load, which means the air-fuel ratio will become either too rich (more fuel) or too lean (less fuel). Here are the key problems to look out for: Poor fuel economy, lack of power, failed emission inspection, rough idle and hard starting. The MAP sensor is a relatively manageable DIY job however, depending on the fitment position of the sensor in your vehicle, some other engine components may need to be removed to gain access. If you are unsure about carrying out a MAP sensor replacement, consult a certified mechanic to avoid further damage.