MAP Sensors measure the level of vacuum (pressure) in the intake manifold and communicates the results to the ECM to determine necessary adjustments to timing and fuel enrichment. Symptoms of a bad MAP Sensor include surging, rough idle, rich fuel mixture, loss of power, poor fuel economy and detonation resulting from a lean fuel ratio combined with excess spark. Regitar-USA products are manufactured to meet or exceed OEM specifications and are tested for quality and performance.