Manifold Absolute Pressure (MAP) Sensor (Peugeot Eurovans 806)

The main engine load sensor is the manifold absolute pressure sensor. A vacuum hose connects the manifold absolute pressure sensor (located in the electronic control unit) (see illustration 5.1) and intake manifold. The pressure is converted by the electronic control unit into an electrical signal. The absolute air pressure in the intake manifold is calculated using the formula: atmospheric pressure minus the pressure in the intake manifold - absolute air pressure in the intake manifold.

When the manifold vacuum is high (in idle mode), then the absolute air pressure in the manifold is very low, and the electronic control unit provides less fuel. When the manifold vacuum is low (the throttle is wide open), the manifold absolute pressure is high, and the electronic control unit provides more fuel.

The intake manifold on MPi models is a "dry" manifold. Because the fuel does not enter the manifold - the fuel injection occurs at the rear of the intake valve - fuel cannot enter the MAP sensor to contaminate the diaphragm, and a fuel trap is not used.

Vacuum values of the absolute air pressure sensor in the intake manifold

Note: All units are in mmHg (mmHg).

State	Vacuum mmHg.
The engine is turned off	Zero
In idle mode	435 - 535
Under heavy loads	Zero
Acceleration	560 - 600

Manifold Absolute Pressure Sensor Type

Internal diaphragm in the electronic control unit

Adjustment

Adjustment of the absolute air pressure sensor in the intake manifold is not possible.

Article based on material from the website: PEUGEOTBOOK

Influence of external factors

• Excess fuel in the fuel trap (if provided for by design) or vacuum hose
• Vacuum leak (intake manifold or other vacuum hoses)
• Vacuum leak in the manifold absolute pressure sensor hose
• The vacuum hose or connection is damaged
• The inlet or outlet valve is faulty
• Incorrect idle speed
• Incorrect ignition timing
• Faulty spark plugs (large gaps)

Checking the Manifold Absolute Pressure Sensor (integrated with the electronic control unit)

1. The performance of the manifold absolute pressure sensor can be assessed using a pressure gauge.

2. Connect a "T" fitting to the vacuum hose that connects the intake manifold to the ECU.

3. Using a short piece of hose, connect the pressure gauge to the "T" fitting connected to the vacuum hose.

Note: The vacuum check must be performed at the hose connection to the manifold absolute pressure sensor. If correct "vacuum" values were obtained elsewhere, this does not prove that the vacuum reached the electronic control unit.

Manifold Absolute Pressure (MAP) Sensor Evaluation

1. Record the results of the "vacuum" values (the engine is turned off) in idle mode, under heavy loads and braking. Compare the obtained values with the values given in the table.



2. If the "vacuum" values are not within the norm, then check:

3. Clogged intake manifold channel leads to a decrease in "vacuum".

4. The vacuum tube is damaged.

5. Leaking diaphragm (inside the electronic control unit).

6. Mechanical failure of the engine, i.e.:

• Vacuum leak.
• Incorrect valve opening or closing timing (adjusting the timing belt)
• The piston rings are worn out.

Checking the diaphragm and vacuum hose of the electronic control unit

1. Disconnect the vacuum hose from the intake manifold. The other end of the hose must be connected to the electronic control unit.

2. Connect the vacuum pump to the pressure gauge by attaching the free end of the vacuum hose.

3. Create a vacuum between 400 and 500 mmHg (mmHg). The MAP sensor must hold the vacuum for at least two minutes.

4. If the sensor does not hold a vacuum, disconnect the hose from the electronic control unit and connect a vacuum pump to the manifold absolute air pressure sensor.

5. Create a vacuum between 400 and 500 mmHg. The MAP sensor should hold the vacuum for at least two minutes. If the sensor does not hold a vacuum, this indicates a faulty diaphragm in the absolute air pressure sensor in the intake manifold. However, if the vacuum persists, this suggests a faulty vacuum hose.

Note: If the diaphragm is faulty, it cannot be replaced separately. The electronic control unit will need to be replaced.

If special equipment is not available

1. Check for vacuum in the intake manifold.

2. Check the vacuum tube for damage and inspect the area where it connects to the electronic control unit for signs of damage.

3. Check the vacuum tube connection to the electronic control unit for leaks and make sure the diaphragm holds pressure.