Air Measurement System

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

Examples: MAF sensor measurement is inaccurate due to a corroded connector, contamination or dirty connector. A contaminated MAF sensor will typically result in a rich system at low airflows (PCM will reduce fuel) and a lean system at high airflows (PCM will increase fuel).