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4 Common Reasons Your Car will Fail Emissions Testing

In order to legally register your car it must pass smog or emissions testing. Modern vehicles have complex emission control systems designed to reduce the hazardous fumes produced by gasoline engines in an effort to protect our natural environment and the air we breathe. If a part of this system is malfunctioning it will cause your vehicle to fail emissions testing and require you to complete some sort of auto repair in order to keep it legally on the road. These are four of the most common reasons for a failed emissions test.


Rich Fuel Mixture

Excessive levels of carbon monoxide will be produced if your car is using more gasoline than necessary. If this is detected during emissions testing your vehicle will fail. This usual reason for this to occur is due to leaking fuel injectors or a faulty Mass Air Flow sensor.


Faulty O2 Sensor

If the oxygen sensor can not properly monitor exhaust fumes to detect how much oxygen is being carried through the engine and out of the exhaust system your vehicle will again begin to use more gas than necessary, as increased oxygen levels will tell the computer to use more gas. The faulty O2 sensor will cause an increase in hazardous fumes being emitted from the tailpipe, which is why the vehicle will fail the test.


Incorrect Fuel Metering

If the computer aided fuel injection or computerized engine control unit malfunctions, the monitoring of the air/fuel mixture will be thrown off, often resulting in excessive fuel burnoff, which will cause the vehicle to fail the test.


Failed EVAP System

The Evaporative Emission Control System (EVAP), is designed to prevent gas vapors from being released into the air. This system will fail due to a leak in a connected vacuum hose or because of a cracked, broken or loose gas cap.


If your car is due for smog testing or needs smog or emissions repair in Morgan Hill, CA, head to Fred’s Foreign & Domestic Car Repair. Our professional auto repair techs utilize the latest diagnostic and repair technology to quickly and accurately service vehicles. We’ll ensure that your car can be safely driven and legally registered. To learn more, or to request an appointment for auto repair in Morgan Hill, give us a call at 408-706-7318. We look forward to helping you with your automotive needs.

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