Saturday, January 31, 2015

Your Car 101 (Series) - What does it mean when they say my vehicle has a misfire?

If your car is running alone in almost a jerking motion, then you may hear from the mechanic that your car has a misfire.  Or maybe you have a check engine code reader that is displaying Cylinder engine misfire.  What does that truly mean?

So basically, whether your car is a 3, 4, 6, or 8 cylinder (or more), there is a specific sequence in which each cylinder operates.  Why?  By alternating when the cylinders produce power, it allows the car to move forward in what feels like a seamless motion.  Let's back up a bit and look at what happens in each cylinder. Each cylinder goes through 4 stages, also called a cycle in the car world.

In the 1st cycle, the intake valve opens, and air enters the cylinder.  Also, fuel is sprayed as a fine mist and the rod moves down to fill the cylinder.

In the 2nd, the rod in a natural motion moves up, compressing the air and fuel mixture.

In the third, the spark plug ignites the air/fuel mixture, shoving the rod down, and producing the power that moves the car.

And lastly, the rod then moves back up, pushing the spent fuel out of the cylinder as the exhaust valve opens.

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All of these events have to work in the perfect sequence in all cylinders.  If all cylinders ran at the same time, then your car would have 100% power during the third stage without any additional power until stage 3 came around again.  Imagine sprinting for 1 minute and taking 3 minutes to slow to a stop then hit a full sprint again. That would be hard on your body, just as it would be bad for the car.  Not to mention a very uncomfortable drive.  The goal is to alternate the cylinders so that it would be closer to a 4 minute jogging period, evening the power throughout the drive.

Now back to the misfire.  When your issue is labeled as a misfire, one of the components caused the third stage to not happen.  Either air or fuel or spark isn't making it into the cylinder.  This could be caused by a number of things, including but not limited to a clogged fuel injector, bad spark plug, or even a severed spark plug wire.  Through this, the mechanic can run through a process of elimination and isolate the problem at hand.


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  2. My husband told me about how he had to take his car to a mechanic because it had a misfire, so I was wondering what that means. It's interesting how all cylinders have to work in a perfect sequence to make a car run smoothly. I can see why it would be hard on my husband's car if they didn't work in sequence, so that would explain why a misfire would happen in the third stage. Now I feel like I have a better understanding of what happened to his car last night. Thanks for posting this!