How MAF Affects Idle
MVS Forums contributor and Volvo wizard jimmy57 explains how the mass airflow sensor affects the air/fuel ratio, idle, mpg and more and various Volvo models.
On Bosch systems that is not really a MAP. It is used for boost pressure monitoring. The earlier extrapolation algorithm where MAF vs engine speed was used for boost level calculation was not as accurate. Primarily it is a feedback sensor used for turbo control valve operation.
On Denso systems where the MAP is manifold mounted it is used for lower throttle load sensing when airflow is low the MAF sensitivity error is larger. Once engine air consumption picks up then manifold pressure sensitivity diminishes and MAF is a better gauge of engine load.
MAP was the only load sensor on strict speed-density fuel systems. Volvo only used that on the Regina/Rex system on the 89-94 740/940 non turbo 230F engines.
The boost pressure sensor on the 99 and later turbo cars with Bosch system usually are noted by boost control codes. The MAF value vs boost pressure indication fall out of mapped value range. It is rarely the pressure sensor is is more likely the MAF sensor.
The MVS Volvo Newsletter is a once-a-month email delivered to your email. It’s simple to unsubscribe at any time if you change your mind.