The MAP sensor reads barometric pressure when the key is first switched on (because this is what’s in the manifold when the engine isn’t running), then switches to measuring manifold absolute pressure after the engine starts. Color that “manifold vacuum,” which is a solid indicator of engine load and needed fuel.
The engine controller uses the initial barometric pressure reading in its algorithms as a baseline and the dynamics of manifold vacuum for engine load and EGR flow. Where there is a mass airflow sensor (MAF) and a MAP sensor, the MAP sensor provides secondary input (like for EGR flow detection) and provides a backup input in case the MAF sensor goes offline.
A MAP sensor fails when:
So what happens when your MAP sensor has gone kaput? Here are the most common consequences:
If your car’s computer inaccurately reads the pressure in the intake manifold as high, the engine will inject more fuel to meet the heightened engine load. This can reduce fuel economy and possibly lead to detonation.
On the flip side, if your car’s computer presumes pressure in the intake manifold is low, it will do the reverse and cut down fuel consumption, therefore leaving the engine with less power for acceleration.
When fuel injection is inadequate, the engine tends to idle rough. There’s also a chance for cylinder misfire to occur.
When the “check engine” light illuminates, it’s possible there’s something wrong with your MAP sensor. This is also the perfect time to check if there’s any problem with the other sensors in your car.
If your MAP sensor is unreliable, chances are, the emissions discharged from your tailpipe will be filled with hydrocarbons, nitrogen oxides, and carbon monoxide. This automatically causes you to fail your emissions test.
It helps to be aware of the signs of a bad MAP sensor so you can act fast to remedy the problem. Or, better be proactive by inspecting your MAP sensor during routine maintenance checkups. You can use a scan tool for this (your MAP sensor reading at idle should have a reference voltage close to five volts) and administer a bench test using a hand vacuum pump and a voltmeter.
Make it a habit to check your MAP sensor from time to time to maintain a sense of balance in your engine’s operation and ensure optimum performance for your car.
If you’ve confirmed that you have a bad MAP sensor, don’t put off shopping for a replacement. The issues it can cause for your ride are no joke, as they can make driving difficult and dangerous. For a high-quality MAP sensor that won’t break the bank, we have you covered here at CarParts.com.
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Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.