Easy step by step instructions on how to correct a vehicle that has failed smog, though appearances may vary, the process is similar for most vehicles.
Difficulty Scale: 4 of 10
Step 1 - One of the most common causes of a failed smog test is the check engine light is "ON" while the engine is running. Learn more
Step 2 - The catalytic converter is a vital part
of the emission control system, when this item starts to fail it will allow high
emissions. (Note: A new cat can overcome a worn or mal-performing engine.)
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more
Step 3 - A misfiring engine causes excessive emissions
to be produced, correcting this problem will help pass a smog inspection.
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Step 4 - Engine tune up's are needed to keep the
engine running efficiently and is a required service on all internal combustion
vehicles.
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Step 5 - A mass air flow sensor or MAF measures
air intake volume and supplies feedback data for the computer which then adjusts
the amount of fuel consumed by the engine. When this sensor becomes contaminated
it can alter the data produced by the sensor.
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Step 6 - An oxygen sensor is designed to measure
the amount of oxygen present in the exhaust system while the engine is running.
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more
Step 7 - An intake vacuum leak can cause an engine
to fail the state smog inspection due to the unmetered air allowed to enter the
engine.
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more
Step 8 - Low cylinder compression can cause an
engine to produce excessive emissions which can be tested using a compression gauge.
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more