Tech Tip Corner
Mass Air Flow Sensor Failure
Premature or Repeated Mass Air Flow Sensor Failure
General Motors Remote Mounted Designs
Instances of repeated Mass Air Flow Sensor failure on General
Motors applications utilizing the remote mounted Delco unit can often
be traced to an engine back-fire condition. The sudden intake pres -
sure buildup can induce cracking of the heated element resulting in
MAF sensor failure.
Several common causes include lean misfire due to low fuel pressure
or restricted fuel injectors, breakdown of the secondary ignition
including internal ignition coil arcing, and a dead spot in the Throttle
Position Sensor (TPS).
A lean fuel condition can be verified by using a scan tool to monitor
the Block Learn memory value with the engine at a steady no load
cruise RPM. A reading above the 135 to 140 range would indicate a
lean fuel mixture, or an exhaust lean above the Oxygen sensor.
Internal ignition coil arcing between the coil primary and secondary
windings can be very difficult to trace. Checking for internal arcing
requires one of the new engine analyzer/scopes.
A dead spot in the Throttle Position Sensor (TPS) can be verified by
monitoring the sensor voltage as the throttle is moved from the idle
position to the Wide Open Throttle position - very slowly - with an
analog voltmeter or lab scope.
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