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Q: Cranks but won't start.

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Cranks but won't start, especially in cool or damp weather. Just replaced the alternator, tensioner and belt and did not fix problem. Mechanic said MAF sensor was dirty, so he cleaned it and problem persists. Occasionally it will start right up, but usually only when weather is warm or vehicle has been used recently. A day or two of inactivity will almost guarantee that it won't start. My next thought was to replace the MAF sensor. What do you think, thanks for your time.

My car has 205000 miles.
My car has an automatic transmission.

A: This may be a sign of a dirty or failing ma...

This may be a sign of a dirty or failing mass air flow sensor. The mass air flow sensor is a unit in the intake system that monitors air intake as it is mixed with fuel prior to being injected into the motor. When this fails, this can cause an imbalanced air/fuel load to be supplied to the motor which results in an over fueling or under fueling situation depending on the conditions. This may cause a hesitation, loss of power or jerking reaction when this sensor is malfunctioning. When this is not working properly, you may also notice a strong smell of fuel. Depending on the make and model of the vehicle and the type of ignition system it uses, this type of symptom can also occur when there is moisture inside the distributor cap causing a misfire as you try to accelerate. I would suggest having a professional from YourMechanic come to your home to diagnose your mass air flow sensor.

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