What causes irregular idling and increased fuel consumption in the 1.6 16V engines of the C3 and C4? Could it be the MAP sensor? Where is it located?

Unstable idling, engine stalling when decelerating, or high fuel consumption are common symptoms of a faulty air metering system. In Citroën TU5JP4 (1.6 16V) engines, air control is performed by… MAP sensor (Manifold Absolute Pressure) combined with IAT sensor (Intake Air Temperature).

• Function: The MAP sensor measures the absolute pressure inside the intake manifold (engine vacuum), and the IAT measures the air temperature. Together, this information is crucial for the ECU (Engine Control Unit) to calculate the air density and, consequently, the correct amount of fuel to be injected.
• Symptoms of Failure:
  1. Oscillating Slow Gear: An incorrect vacuum reading causes an unregulated air/fuel mixture.
  2. High Consumption: A faulty sensor may indicate a lower pressure (weak vacuum) than the actual pressure, causing the ECU to inject more fuel.
  3. Check Engine Light On: With an error code related to manifold pressure (usually P0106, P0107, or P0108).
• Location and Solution: The MAP sensor is located in Intake Manifold. The problem is usually caused by dirt or internal wear. The solution involves replacing the sensor and, in some cases, cleaning the… butterfly body (TBI) to ensure unimpeded idle airflow.