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What to Do When Your “Check Engine” Light Comes On

You turn on your car and you start to panic. You see the Check Engine light lit on your dashboard. It came out of nowhere and it doesn’t share specifics. But no need to panic – the light doesn’t mean your engine is about to blow. There are several very common reasons that the engine light come on.

1 – Loose or Faulty Gas Cap

A gas cap doesn’t seem very important, but it actually is.  When a gas cap is loose or cracked, fuel vapors leak out of the tank and this can affect the fuel system. This causes a reduction in gas mileage and increases emissions.

What you should do: If your car isn’t feeling jerky or strange when the check engine light comes on, the first thing you should check is the gas cap. If driving, pull over, retighten it, and take a look at the cap to see if it has any cracks. Watch to see whether the Check Engine light turns off. Continue driving and see if the check engine light turns off.  If so, you’re good to go! If not, take your vehicle to a qualified mechanic to have them check for the other issues discussed below.

2 – Replace Oxygen Sensor

An oxygen sensor is a part that monitors the unburned oxygen coming from your vehicle’s exhaust and helps monitor how much fuel is burned. Most cars have two to four oxygen sensors and the code you get from the scanner tells you which one needs replacing. A faulty sensor can fail to provide the right data to the computer which can cause a decrease in gas mileage and increase emissions.

What you should do:  A mechanic can tell you whether an oxygen sensor is malfunctioning and get it replaced.  That’s far better than not replacing a broken sensor that can eventually lead to a broken catalytic convertor which can cost into the thousands.

3 – Replace Spark Plugs and Wires

Spark plugs seal the combustion chamber and provide a gap for a spark to jump across and initiate combustion in the engine. When spark plugs are failing, the plugs misfire. A jolt in a car’s acceleration usually occurs when this happens. Older cars (those made prior to 1996) should be replaced every 25,000-30,000 miles. Newer vehicles can last up to 100,000 miles.

What you should do: A mechanic can check your spark plugs to see if they are functioning as they should. If not, it’s important to get them replaced right away. Replacing spark plugs is easy and cheap and your car will run better.

4 – Replace Mass Airflow Sensor

The mass airflow sensor tells the vehicle’s computer to add the proper amount of fuel based on the air flowing through to the engine. A faulty mass airflow sensor can increase emissions, cause the car to stall, and decrease gas mileage. Failing to replace air filters can cause airflow sensor problems.

What you should do: In theory, you can drive for a few weeks or even longer with a broken MAF sensor. However, you will notice a decrease in gas mileage and over time the car will eventually start stalling a lot. A good mechanic can determine whether the MAF sensor needs to be replaced. If so, it’s wise to get it replaced in the near future.

5 – Replace Catalytic Convertor

The catalytic convertor works to reduce exhaust gases. It converts carbon monoxide and other harmful materials into harmless compounds. Catalytic convertors shouldn’t fail if you’re maintaining your vehicle well.  If your catalytic convertor does fail, you’ll notice a significant decrease in gas mileage, your car won’t go any faster when you push the gas, and ultimately, your vehicle will quit running.

What you should do: Have a qualified mechanic check your catalytic convertor. If it has indeed failed, you will need to get it replaced. This repair is costly, but necessary.

Plenty of other possibilities for a check engine light exist, but the above five are the most common. Always check the gas cap first as that is often the problem and is and easy (and inexpensive) fix. If the gas cap isn’t the problem, a qualified mechanic is your best bet to get to the root of the problem.

Whether it’s your Check Engine light or something else, Roemer’s Tire Factory is your trusted source for auto repair and maintenance in Missoula. Just give us a call at (406) 529-6425 to schedule an appointment. As always, you’ll get top-quality customer service. See our reviews here.

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