What Does The Map Sensor Do? (Ford E-150, E250, E350)

Your Ford E150 (E250, E350) comes equipped with a manifold absolute pressure (MAP) sensor. It's a key component of the fuel injection system and one that your vehicle's fuel injection computer relies on heavily to keep the engine running optimally.

In this article I'm gonna' answer the most commonly asked MAP sensor questions. I've also included the link to the MAP sensor tutorial you'll need to test it.

APPLIES TO: This tutorial applies to the following vehicles:

• Ford E150: 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996.
• Ford E250: 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996.
• Ford E350: 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996.

What Does A MAP Sensor Do?

In a nutshell, the MAP sensor's job is to measure the amount of pressure inside the intake manifold and report it to the fuel injection computer.

The fuel injection computer then uses this information to calculate the air density inside the intake manifold. With this calculation it can now determine the amount of air that's entering the engine.

Now to give you a bit more technical detail, the fuel injection computer in a speed density type fuel system (like what is in your vehicle) needs to know the following to calculate the amount of air entering the engine so that it can then calculate the amount of fuel to inject into it:

1. Engine speed.
2. Intake Air temperature.
3. Engine load (intake manifold pressure).

What Happens When A MAP Sensor Goes Bad?

When the MAP sensor fails and stops reporting the intake manifold vacuum pressure, the fuel injection computer won't be able to determine the amount of air entering the engine.

Without this information, it won't be able to calculate the correct amount of fuel to inject into the cylinders.

From this point on, the bad MAP sensor will cause several driveability, engine performance, and emissions problems. The next section will expound on these.

What Problems Can A MAP Sensor Cause?

When a MAP sensor fails, you're going to see one or more of the following symptoms:

1. Bad gas mileage.
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.
6. The engine may start and immediately stall.
7. The engine has to be cranked longer than usual for it to start (this is called extended cranking).
8. A heavier than normal exhaust smell when the engine is running.
9. Won't pass the emissions test.

How Can You Tell If A MAP Sensor Is Bad?

Testing the manifold absolute pressure (MAP) sensor is the surest way to find out if it has failed and is the cause of the engine performance or drivability problem you're currently experiencing.

See the next section to find out more.

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

A MAP sensor can easily be diagnosed as bad by doing a simple multimeter diagnostic test.

Here's the basic MAP sensor test procedure:

• Checking for MAP sensor trouble codes with a code reader or scan tool.
• Making sure that the MAP sensor is receiving 5 Volts DC.
• Making sure that the MAP sensor is receiving Ground.
• Making sure that the sensor's MAP Hertz frequency signal increases/decreases as vacuum is applied/released to it.

If the MAP Hertz frequency signal does not increase/decrease as you apply/release vacuum to the MAF sensor, then you can conclude that your Ford E-Series van's MAP sensor is bad and needs to be replaced.

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

• Manifold Absolute Pressure MAP Sensor Test (Ford 4.9L, 5.0L, 5.8L).

Can I Drive My Van With A Bad MAP Sensor?

Depending on the severity of the symptoms the bad MAP sensor is causing, you may not be able to safely drive the van.

Even if it's possible to drive your van (with a bad MAP sensor), you should avoid doing so.

Why? Because 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:

1. Damage to the catalytic converter.
2. Accelerated wear and tear on the piston rings.
3. Fuel will seeping into the crankcase (across the pistion rings) that will eventually start to dilute the engine oil.

If the MAP sensor is causing the fuel injuection computer to inject less fuel, then you risk:

1. 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.

Any electronic fuel injection system problem should be diagnosed and resolved as soon as possible.

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 E150, E250, and E350 Tutorials

You can find a complete list of tutorials for the full-size Ford E-Series vans here: Ford 4.9L, 5.0L, 5.9L Index Of Articles.

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

• Manifold Absolute Pressure MAP Sensor Test (Ford 4.9L, 5.0L, 5.8L).
• Ignition Coil Test -No Spark No Start Tests (Ford 4.9L, 5.0L, 5.8L).
• How To Troubleshoot A No Start (Ford 4.9L, 5.0L, 5.8L).
• Testing A Blown Head Gasket (Ford 4.9L, 5.0L, 5.8L).
• How To Test Engine Compression (4.9L, 5.0L, 5.8L).