Air Measurement System

With this condition, the engine may actually run rich or lean of stoichiometry (14.7:1 air to fuel ratio) if the PCM is not able to compensate enough to correct for the condition. One possibility is the mass of air entering the engine is actually greater than what the mass airflow (MAF) sensor is indicating to the PCM. For example, with a contaminated MAF sensor, the engine runs lean at higher RPM because the PCM delivers fuel for less air than is actually entering the engine.

With this condition, the engine may actually run rich or lean of stoichiometry (14.7:1 air to fuel ratio) if the

PCM is not able to compensate enough to correct for the condition. One possibility is the mass of air entering the engine is actually less than what the MAF sensor is indicating to the PCM. For example, with a contaminated MAF sensor, the engine runs rich at idle because the PCM delivers fuel for more air than is actually entering the engine.