If your engine is sputtering, find out how to tell if it’s the spark plugs and how worn spark plugs or plugs with a bad gap can cause this with tips from our expert mechanic Sue.
How Worn Spark Plugs Can Cause Engine Sputtering
Worn Spark Plugs Causing an Engine Misfire
Today, many spark plugs are made of platinum or iridium and can last up to 120,000 miles. You may not be paying attention to when they’ll wear out since they don’t need to be changed as often.
Fuel enters from the fuel injection ports through the intake ports. A valve opens and sprays the fuel into the cylinder as the piston moves up and down, and as it compresses it puts compression inside. As the piston moves up, the spark ignites at the spark plug, lighting up the fuel and pressing the piston down to push and spin the crank to move the vehicle forward. Then the exhaust valves open, and smoke expels out the tailpipe. When there’s a misfire you’ll hear the skip every time the exhaust valve opens, which can travel out the exhaust port and to the tailpipe.
Spark Plug Gap Is Too Wide
Manufacturers’ spark plugs are set for the voltage the ignition coil has for each cylinder. If the spark plug gap is too wide, the spark will be weak, leaving more fuel in the cylinder. The fuel wont burn as quickly, and next to come is detonation knocking and poor fuel mileage. The fuel will waste out the tailpipe, can clog the catalytic converters, and cause other damage.
How to Check a Car with an Engine Sputtering
Steps to check a car with an engine sputtering
- Turn the Car on, Let the Engine Idle, and Listen for Skipping
If you suspect you have a misfire but no check engine light, turn the car on and let the engine idle. This way you can listen for any skipping. Some cars will turn on the check engine light after a certain amount of skips have registered.
- Check for Tailpipe Rattling
With the vehicle idling, check the tailpipe and see if the engine sputtering is accompanied with an engine rattle, which is a sign the engine could be misfiring.
- Feel for Skipping While Driving
See how the car feels while driving, and listen or feel for the engine skipping, which is a sign of a misfire.
How-to Videos Install Your Own Spark Plugs and More
Learn how to install your own spark plugs with our how-to videos. You can find videos for repairs on specific models in our how-to video library. Before installing the spark plugs, you can check and adjust the gap with a spark plug gap tool.