Not Sure When to Change Spark Plugs? Look for 6 Signs

  • Apr 4,2018
Not Sure When to Change Spark Plugs? Look for 6 Signs Not Sure When to Change Spark Plugs? Look for 6 Signs

Many drivers assume that when their car has trouble starting, there’s a problem with the battery. While this certainly could be the case, it’s not the only possibility. Old or faulty spark plugs could be the culprit! After all, these small spark plugs have a big job to do. Learn why it’s important to keep this part of your car in great working order and when to change spark plugs by watching for these bad spark plug symptoms.

Changing spark plugs could be a good idea when...

1. Your check engine light comes on.

Worn/failed spark plugs, coil packs, or spark plug wires can trigger your check engine light to come on. In today's cars, say Firestone Complete Auto Care technicians, if a plug starts to fail then the most obvious event should be the check engine light coming on or even flashing.

This can cause your engine to misfire and your check engine light to pop on. A flashing engine light could mean that potentially catastrophic misfires are taking place, say our technicians.  

In general, it's best to replace spark plugs as part of preventative maintenance based on manufacturer's specifications. This can help save you from costly repairs, as driving with misfiring spark plugs could put undue stress on your car's catalytic converter (the engine's exhaust cleaner).

Symptoms of misfiring spark plugs include rough idling, uneven power when accelerating, and an increase in exhaust emissions. 

Note that a check engine light could be potentially caused by a number of things, not just a spark plug problem. That's one reason your local Firestone Complete Auto Care offers Code Scans, which reveal any codes that indicate a misfire due to a spark plug failure. Since our facilities provide complete auto care, our technicians also have the proper tools and expertise in engine control systems, sensors, and on-board diagnostics to perform an advanced diagnostic and provide an accurate repair estimate. 

2. Your car has trouble starting.

Your spark plugs have one of the most important jobs in your vehicle, which is to provide the spark that powers the engine! Old, worn out spark plugs have a harder time creating the spark that actually powers your engine. If your car stalls when you are trying to turn it on, there could be a problem with spark plugs or damaged spark plug wires. The battery is most likely the culprit if your car has no power and won't start at all.

3. You’re filling up the gas tank more often.

If your spark plugs are on their last leg, they’ll take it out on your gas mileage. Worn out spark plugs can increase your vehicle’s fuel consumption because they won’t effectively burn the fuel that goes into the engine, meaning you’ll be shelling out more money on fill-ups. 

"A misfiring spark plug can reduce fuel efficiency by as much as 30%," reports the National Institute for Automotive Service Excellence.

In general, keeping your car tuned up can work wonders for your fuel efficiency. 

"Fixing a car that is noticeably out of tune or has failed an emissions test can improve its gas mileage by an average of 4%," reports

4. The engine idles roughly (and you can hear it!).

Typically (hopefully!) your engine probably purrs like a kitten, but turn down your music and take a listen. If you notice that the engine is making rattling, pinging, or knock-like noises, your spark plugs might be to blame.

5. Your car won’t accelerate quickly.

You’re probably pretty familiar with how your vehicle handles and drives. If you notice that your car isn’t as responsive as normal, particularly when you’re trying to accelerate, this could be traced back to worn spark plugs. It might be time to have them replaced – no one likes driving a sluggish, fuel-guzzling car.

6. Per the manufacturer, it's time!

In any car care matter, it's always best to follow the Manufacturer Suggested Maintenance Schedule. Review your vehicle's suggested maintenance schedule to see when to replace your spark plugs. 

Luckily, spark plugs don’t wear out very quickly. You can typically get 80,000 miles on them before they need replacing. But if you notice any of these symptoms, it’s time to get your spark plugs checked out with an engine tune up.

Continuing to drive on worn out or damaged spark plugs can ultimately cause engine damage, so don’t put it off. Make an appointment at your local Firestone Complete Auto Care so our expert technicians can see exactly what’s going on!

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