Engine on a Volkswagen.

What causes an engine misfire?

In Vehicle Maintenance by HomeTowne Auto Repair & Tire

It’s important to note any abnormal sounds and behaviors when using your vehicle. These symptoms may indicate an underlying issue that could grow worse overtime. 

Engine misfires are a significant problem that you should be aware of.

What is an engine misfire?

An engine misfire is when the air in the fuel isn’t ignited correctly, which leads to a decrease of engine performance. It could be computer, electronic or mechanical related.

What are signs that an engine is misfiring?

The check engine light turning on is one sign of a misfire. However, you shouldn’t assume that your car is misfiring just because this icon illuminated. A check engine light may also come on for other reasons, like being low on oil or catalytic converter problems.

Check engine light on Kia Optima.

Other symptoms include a vehicle running rough and stalling.

Your vehicle may seem to have trouble accelerating or stuttering. If it’s bad enough, it might feel as though it’s stumbling.

On a really bad misfire, you could get a popping sound through the intake manifold.

What causes an engine to misfire?

Components that have gone bad, including ignition coils and spark plugs, may result in an engine misfire. A bad timing belt or fuel injector might be the culprit too.

Spark plugs.
Spark plugs

A vehicle needs to have the right amount of air and fuel. Misfires can occur if there is too much or too little air or fuel.

Timing plays a role, as well. If the timing isn’t in line, then the camshaft sensor and crankshaft sensor aren’t able to communicate.

Another cause behind a misfire is a mechanical engine problem. There could be camshaft lobe wear, a rocker arm issue, a valve problem, or a mixture of the three. Maybe the valves aren’t opening and closing the way they should.

An engine misfire could even be caused by contaminated fuel, or it might be the result of a malfunctioning sensor that’s preventing the computer from igniting the fuel or controlling the spark correctly. 

How do we figure out what’s causing an engine misfire?

We perform diagnostic testing to determine why a misfire is occurring. 

Diagnostics can be anything from hooking up the scan tool and reading the codes from the computer, helping indicate that a misfire is being picked up. It may not tell you the underlying issue, but you have an idea of what cylinder to start on. 

It’s not uncommon for there to be a misfire and not have any codes. It’s also possible to get a code for something else and not a misfire code. Another sensor may be picking up something outside of the typical parameters and flagging for a code. That’s why it’s important to look into it – it’s not always clear cut.

What happens if you ignore a misfire?

If you believe your car’s engine is misfiring, it’s very important to have it checked out by a mechanic or auto repair shop as soon as you can. The problem could start happening more frequently or worsen if you don’t.

In fact, misfires that aren’t addressed can negatively impact the catalytic converter – a very expensive part that helps cut down on pollution. The items that this component is made up of change exhaust gasses from bad to good. 

When you have a misfire and you’re getting raw fuel or rich conditions in the exhaust, the catalytic converter gets really warm and starts melting from the inside out. When that happens, it can prevent air in the exhaust from being released.

HomeTowne Auto Repair & Tire is an authorized Michelin and BFGoodrich tire dealer located in Woodbridge, Virginia. Automotive repair services are performed on all makes and models, including oil changes, brakes, alignments, inspections, and computer engine diagnostics.