Symptoms of a Bad Mass Air Flow Sensor on a Tacoma

by Steven Symes
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Since Toyota Tacoma's have fuel-injected engine, it also has a mass air flow sensor. Mass air flow sensor's measure the amount of air coming into the engine, aiding the Tacoma's computer in making adjustments to achieve an optimal air/fuel mix in the engine's cylinders. Like all sensors, mass air flow sensors can go bad, but there are symptoms to indicate this has happened.

Check Engine Light

A bad mass air flow sensor should set off the truck's check engine light. The check engine light on the dash of your Tacoma will illuminate each time a sensor detects an abnormality with the truck or the sensor itself has gone bad.

Lean or Rich

If, upon starting your Tacoma, you see smoke coming from the tailpipe of the truck, even if only for a moment, that is a sign your Tacoma is likely running rich. If the RPMs of your Tacoma seem to fluctuate erratically, it could be a sign your truck's engine is running lean. Removing the spark plugs from the engine will confirm if your Tacoma is running lean or rich. If the spark plugs are coated with a black or gray soot the engine is running rich. If the spark plugs are coated with white then the engine is running lean.

Rough Engine

If your Tacoma has a bad mass air flow sensor, it can cause the engine to run rough. After starting up your truck the engine may stumble and recover or it could stall out completely, requiring you to restart the engine. If there is a delay from when you push on the accelerator and when the engine begins to accelerate that can also be a sign of a bad mass air flow sensor. While sitting at stop lights if you notice the engine is idling rough a bad mass air flow sensor may be the cause.

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