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3 Reasons Your Car Failed the Emissions Test

Car Exhaust Emission Test
Concerns about the environmental impact of automobile exhaust has grown, so many states have implemented stricter emissions standards. Cars that fail to meet current standards may be deemed ineligible for legal use. Regular emissions testing has become a regular part of many people's lives.
Unfortunately, owners don't always know exactly why their car failed an emissions test. Even those who don't live in states with mandatory emissions tests should understand the factors that can lead to dangerous exhaust rates. This article takes a closer look at three things that can cause a car to fail an emissions test.
1. Lit Check Engine Light
To many people, the factors involved in emissions testing remain a mystery. Yet one clear-cut clue exists about whether your car will pass or fail the test. If your dashboard check engine light happens to be lit, your car is almost guaranteed to fail the emissions test. To understand why, it helps to know more about how emissions tests work.
In the past, testing a car for emissions involved attaching special sensors to your tailpipe and running the engine to determine the particular exhaust composition. This approach proved quite laborious. Fortunately, for cars produced since 1996, the testing process runs much more smoothly. A technician simply hooks up a diagnostic tool to your car's computer.
The computer in a modern car receives information from a variety of different sensors. Many of these sensors monitor the composition of the exhaust produced by your engine. If these sensors detect erroneous levels, many of them trigger the check engine light to come on. In fact, for many cars, only emissions-related problems can trigger the check engine light.
Fortunately, the opposite rule also holds true. If your check engine light isn't lit, your car stands a good chance of passing the emissions test. Those with lit check engine lights can save themselves time by scheduling a trip to the mechanic before they go for their emissions test.
2. Rich Fuel
As noted above, a wide variety of issues can trigger your check engine light to come on. Unless the true problem receives an accurate diagnosis and repair, your car will remain unable to pass the emissions test. One of the most common triggers for a check engine light involves an overly rich fuel mixture.
In order to provide optimal efficiency, and keep emissions as low as possible, the mixture of air and fuel entering your engine must remain perfectly balanced. When mechanics refer to a fuel mixture as rich, they mean that the mix contains too much gasoline relative to the air. A larger proportion of this gasoline fails to combust, instead passing out through your exhaust.
A car's fuel mixture may become rich for a number of reasons. One frequent issue involves a faulty or failed oxygen sensor. Problems with pressure regulators, fuel injectors, and engine coolant temperature sensors can also lead to rich fuel. Aside from triggering your check engine light, rich fuel also commonly manifests as black exhaust.
3. Bad Spark Plugs
Another common source of elevated emissions levels involves your car's spark plugs. As you probably know, the spark plugs generate the jolt necessary to combust the fuel mixture inside your engine's cylinders. If a spark plug fails to generate a spark, the fuel won't combust. As a result, your exhaust will contain higher levels of hydrocarbons and carbon monoxide.
Spark plugs often fail as the result of carbon that builds up on their surface, preventing spark formation. Mechanics usually refer to this phenomenon as fouling. Likewise, spark plugs may suffer internal damage or damage to their wiring systems. Such problems usually necessitate the installation of new spark plugs.
Failing an emissions test can create a lot of stress. For more information about how to get your car running clean before your next emissions test, please contact the auto experts at Broadway Motors Inc.