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Summary
  • A severe case of engine misfire may cause vehicle shaking and trigger the check engine light.
  • An engine misfire occurs when there’s incomplete or zero combustion in one of the cylinders.
  • It’s never safe to drive when your car is shaking. Doing so can damage the catalytic converter and other costly parts.
  • There’s an endless list of reasons why your engine could misfire. Have a trained professional check your vehicle to get an accurate diagnosis.

The dreaded check engine light (CEL) is always worrisome whenever it turns on. But when the light illuminates (or starts to flash) and your car begins to shake, that makes the situation even more stressful. Naturally, you’ll want to find out what’s causing the problem and how to address it. There are literally dozens of reasons misfires can happen, so we’ll just hit the highlights.

What Causes the Check Engine Light to Flash and Make the Car Shake While I’m Driving?

Usually, when the check engine light is flashing and the car is sputtering and shaking, that means you’re dealing with an engine misfire serious enough to possibly damage the catalytic converter and in most cases the PCM/ECM will kill the injector to prevent that. Basically, the check engine light comes on whenever there’s an issue that could increase vehicle tailpipe emissions.

An engine misfire—a problem that almost always causes an increase in hydrocarbon emissions —is one of the many reasons why the check engine light might illuminate (or start to flash). A misfire occurs when there’s incomplete (or zero) combustion taking place inside one of the engine’s cylinders.

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When one cylinder isn’t providing turning power to the crankshaft when it’s time for that cylinder to fire, the crankshaft will slow down during that cylinder’s lack of a power event. When a misfire is severe enough, you may notice that the engine begins to shake.

image showing the power balance function of a scan tool
Higher end scan tools have a power balance function like the screenshot you see in this illustration, with the downward track indicating rpm loss on the misfiring cylinder. | Image Source: Richard McCuistian

Pro Tip: The fewer cylinders your engine has, the more you’ll feel it when one is misfiring. 

On a V8, you may simply notice a loss of power and a flashing check engine light. 

On a four cylinder it may feel like your steering wheel is attached to a machine gun. Misfires can happen intermittently, at idle only, accelerating only, or under heavy load (in 4th gear at 45 mph). They can be random or regular. Misfires can happen on just one cylinder or on several different cylinders at the same time. They can happen right after the engine is started and then clear up due to coolant seeping into a single cylinder.

And there are several reasons why misfires can happen.

It’s important to point out that an engine needs three primary ingredients to run properly: a precise air-fuel mixture, adequate spark, and good compression. When any of these factors are missing, incomplete combustion occurs, resulting in a misfire.

Pro Tip: Spark plugs that are gapped too close or partially fouled may cause a random misfire that only happens at idle. This kind of misfire can be felt best at the exhaust pipe with a rag. The exhaust will “puff” with each misfire.

There are many potential causes for a misfire, some of the most common of which include:

Spark plugs that are gapped too close or partially fouled may cause a random misfire that only happens at idle. This kind of misfire can be felt best at the exhaust pipe with a rag. The exhaust will “puff” with each misfire.

Richard McCuistian, ASE Certified Master Automobile Technician

In other words: There is an almost endless list of reasons why your engine might be misfiring, causing the check engine light to turn on and the car to shake.

See also  How to Replace a Faulty Crankshaft Position Sensor

FAQ

Is It Safe to Drive When Your Car is Shaking and the Check Engine Light is  Flashing? 

You should not continue to drive when the car is shaking and the check engine light is on. Such a scenario often indicates that your car is suffering from a severe misfire, which could damage the catalytic converter and other costly components.

How to Fix a Check Engine Light Flashing with the Car Shaking

There are multiple reasons why your engine might be misfiring badly enough to cause a check engine light and shaking. Therefore, there isn’t a magic bullet fix for the issue. The solution for a Kia Optima shaking when idle might be different from a Prius engine shaking while starting. If your car started shaking or your car is shaking when starting up, you (or your mechanic) will need to diagnose the problem, then perform the necessary repairs.

result of a burnt car valve
The steps to fix a misfiring engine will be different depending on the diagnosis. For example, a burnt valve will cause a loss of compression and a steady misfire, but the head has to be removed to take care of a problem like the one shown in the photo. | Image Source: Richard McCuistian

Where to Get Replacement Parts for Your Ride

Because there are many potential causes for engine misfires, fixing the issue can prove challenging. Good thing you can find exactly what you need here at CarParts.com without any hassle.

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We have an extensive selection of replacement parts, ensuring a quick and convenient solution to get you back on the road. Eliminate the need to visit multiple physical stores in search of replacement parts. Our catalog covers everything from ignition system components to emissions equipment parts.

Simply search for the part you need, use the vehicle selector to view compatible parts, and change the filters to your needs. It’s that easy. Our products come with a low price guarantee, so you won’t have to break the bank to repair your ride.

We also guarantee quality. Not only do we source our parts from top brands but all our products are also stringently tested during manufacturing to ensure they comply with industry standards.

Don’t let faulty components ruin your trip. Check out the replacement parts you need and order today!

About The Author
Written By Automotive Subject Matter Expert at CarParts.com

Mia Bevacqua has over 14 years of experience in the auto industry and holds a bachelor’s degree in Advanced Automotive Systems. Certifications include ASE Master Automobile Technician, Master Medium/Heavy Truck Technician, L1, L2, L3, and L4 Advanced Level Specialist. Mia loves fixer-upper oddballs, like her 1987 Cavalier Z-24 and 1998 Astro Van AWD.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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herbert miller

since i found carparts.com my affair with cars has improved dramatically! I ordered from you recently and was so impressed with ur prompt delivery to my door no less, i turned jason of jason’s garage, my mechanic in heber city, utah onto you all. He has been very disappointed with his parts supplier and their long delivery times. I will be seeing him thursday to try to nail down whats ailing my kia 2004 optima lx. the strut/shocks i got from you, he put in but was impressed with price and delivery time. every two weeks i drive to nevada from park city. The front of the car started to shake at 80mph on I-80 after making the trip several times with no problem. One & half hours on the road, the shaking started and stopped when i hit 50mph. After he put struts in it was fine for 3 trips but this last trip it started again, so we’ll see if we have a clue. Also i burn a half quart of oil each trip and if im idling for 5-10mins and get moving again, a cloud of white smoke pours out exhaust for 3mins.

herbert miller

i dont know where to find policy but i’m sure i agree

Hello Herbert,

Thank you so much for the positive feedback! We’re glad you and your mechanic have been happy with our parts and service. As for the problems with your car, the shaking could be something as simple as a wheel balance problem. The burning oil and white smoke are likely linked to something more severe, however. You can learn more by reading this article: https://www.carparts.com/blog/white-smoke-from-exhaust/

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