What Does The MAP Sensor Do? (Ford F150, F250, F350)

The engine in your F150 (F250, F350) uses a speed-density type fuel system. As such, it comes equipped with a manifold absolute pressure (MAP) sensor.

In this tutorial I'll answer some of the most common MAP sensor questions. I've also included a link to the tutorial that'll help you test it.

APPLIES TO: This tutorial applies to the following vehicles:

  1. Ford Bronco: 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996.
  2. Ford F150: 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996.
  3. Ford F250: 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997.
  4. Ford F350: 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997.

What Does A MAP Sensor Do?

The manifold absolute pressure (MAP) sensor's job is to let your vehicle's fuel injection computer know the pressure inside the intake manifold.

The fuel injection computer then uses this information to calculate the air density inside the intake manifold and determine the amount of air entering the engine.

Once the fuel injection computer has determined how much air is entering the engine, it can now inject the correct amount of fuel into the engine's cylinders.

MAP sensors are usually installed in speed-density type fuel systems. In this type of fuel system, the fuel injection computer needs to know the engine load, the intake air temperature, and engine RPM to determine the amount of air entering the engine so that it can then calculate the correct amount of fuel to inject.

What Happens When A MAP Sensor Goes Bad?

When the MAP sensor fails, the fuel injection computer won't be able to calculate engine load and thus won't be able to determine the amount of air entering the engine.

This in turn will cause the fuel injection computer to either inject too much fuel or not enough. You will see excessive fuel consumption, poor fuel economy, and possibly have the engine backfire through the intake manifold.

You're also going to see the check engine light illuminated on your vehicle's instrument panel. The check engine will be illuminated by one or more MAP sensor trouble codes.

What Problems Can A MAP Sensor Cause?

A bad manifold absolute pressure (MAP) sensor can cause several different symptoms:

  1. Bad fuel economy.
  2. Lack of power.
  3. Black smoke coming out of the tailpipe.
  4. Check engine light is illuminated by one or more MAP sensor trouble codes.
  5. Engine suffers a very rough idle, the engine my start and immediately stall.
  6. The engine has to be cranked longer than usual for it to start (this is called extended cranking).

How Can You Tell If A MAP Sensor Is Bad?

When a MAP sensor fails, engine performance is going to suffer. This in itself isn't sufficient information to pinpoint the engine performance problem or drivability problem to the MAP sensor.

What you'll need to do, to find out if the MAP sensor is bad, is to perform a basic diagnostic on the engine's fuel system.

This basic fuel system diagnostic includes: checking for MAP sensor trouble codes. Applying vacuum pressure, via a vacuum pump, to the MAP sensor to see if its voltage signal changes.

How Can I Find Out If The MAP Sensor Is Bad?

The MAP sensor can easily be tested to find out if it's bad or not.

In a nutshell, vacuum pressure is applied to the MAP sensor and then a multimeter reads its voltage signal.

The following tutorial will help you to test the MAP sensor using a vacuum pump and a multimeter:

Can I Drive My Pickup With A Bad MAP Sensor?

In most cases, it is possible to drive the car with a bad MAP sensor. But this should be devoted.

Here are the reasons why:

When the MAP sensor fails, it's either going to cause the fuel injection computer to inject too much fuel or not enough.

If too much fuel is being dumped into the engine cylinders, you risk damaging the catalytic converter. You also risk accelerating the wear and tear on the piston rings.

If you drive the vehicle long enough, this extra fuel will seep into the crankcase (across the pistion rings) and will start to dilute the engine oil.

If the MAP sensor is causing the engine to not receive enough fuel, then you risk damage to the cylinder intake and exhaust valves. This is due to the fact that the engine is running on a lean air fuel mixture that will cause the cylinder head valves to run hotter than usual.

Where To Buy The MAP Sensor And Save

You can find the MAP sensor in any auto parts store. If you're wanting/needing to save a few bucks, then buying the MAP sensor online is the route to take.

The following links will help you comparison shop for the MAP sensor:

More Ford F150, F250, F350 Tutorials

You can find more tutorials Ford F150, F250, and F350 in the following index:

  1. Ford 4.9L, 5.0L, 5.8L Index Of Articles.

Here's a sample of the tutorials you'll find in the index:

  1. How To Test The Ford Ignition Control Module (Distributor Mounted).
  2. How To Test The Ford Ignition Control Module.
  3. Throttle Position Sensor (TPS) Test (Ford 5.0L, 5.8L).
  4. How To Test The Ford Mass Air Flow (MAF) Sensor.
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Pontiac Vehicles:

  • Grand Am 3.3L
    • 1992, 1993