If One Fuel Injector Is Bad Should I Replace Them All?

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Previously we have written an article on how to fix misfire engine. As a recap, one of the culprits for the misfiring engine is a faulty fuel injector. You may need to replace it if it is found to be leaking or bad. A car generally has one fuel injector per cylinder. So the question is if one fuel injector is bad should you replace them all?

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Getting fuel injectors replaced can sometimes cost hundreds of dollars in labor if you don’t do it yourself, making it quite expensive. Let’s find out if it’s worth replacing just one fuel injector or replaces the whole set.

If One Fuel Injector Is Bad Should I Replace Them All?

Depending on several factors, it may be possible to buy just one new injector. But that depends on your particular situation. Here are some of the factors:

  • Mileage and age of the car
  • Budget
  • Cause of fuel injector failure
  • Your skill should you choose to DIY

Mileage and age of the car

If the vehicle is new, it may only need a minor repair to replace one injector. When we say “new” it means the car is a few years old and the mileage is 50,000 miles and below.

However, the cost of replacing one fuel injector can be expensive and not all manufacturers make it easy to replace an injector.

If the car’s engine is over 10 years old or has over 100,000 miles on it, a single injector failing could mean that the others are old and on the verge of failing as well.

Rarely will more than one injector fail at the same time. A good diagnostic mechanic should check the whole system because other parts could be the cause (plugged fuel delivery lines or broken wires in the injector harness etc.)


You can expect to pay between $350 and $850 on average for one set of fuel injectors. A range of factors affects the cost to replace a fuel injector. Smaller vehicles with fewer cylinders will require less expensive parts and come in at the lower end of this spectrum.

Larger, high-performance engines command higher prices for replacement parts and labor because these cars typically need more time on shop racks when getting fixed up as well due to their complexity levels.

If you’re low on funds and still have time to spare, it’s unwise to spend more money unless you know for sure that you need to. But if a couple of hundred dollars won’t bother you much, it’s worth the investment.

Cause of Fuel Injector Failure

Injectors typically last a long time and only fail when there is an underlying cause. These are rare, but the longer you keep your vehicle running, the more likely it is that you will have to deal with one.

One way to make sure there are no underlying issues is a thorough diagnosis of the fuel injection system. You have to make sure that there are no problems with the fuel pressure regulator, wiring harness, or injector driver module before you replace the failed injector.

It is important to do this because there could be an underlying cause that may come back to bite you later.

Your skill should you choose to DIY

According to YourMechanicfuel injector replacement needs specialized cleaning and test equipment.

If you are not confident that you have the knowledge and tools to do it, you should find someone who does. We’ve seen people who don’t have the necessary skills or discipline replace parts they don’t need, which then cause issues because of their improper installation.

It would be a pain to have everything taken apart and then put back together, only for the problem to still exist or even get worse. Now you get to try and see if it was something that you messed up or misplaced, or if the part you replaced was bad.

How to tell if a fuel injector is bad?

There are many things to look for to determine if your fuel injector is bad. Some of the symptoms are the following:

  1. The check engine light is on
  2. The car idles rough
  3. You can smell gas
  4. Engine misfire

It is important to diagnose the problem before you replace your fuel injectors. Knowing what is causing the problem will help narrow down the possible cause.

If one of these signs is present, then it is a good idea to have a certified mechanic check out your vehicle. And inspect all components that could be causing the trouble. They can pinpoint the exact source of the issue and will be able to replace the part that is causing the problem.

You can use an OBDII scanner to get a code for the injector to narrow things down. If the code is for a specific injector, then that is the issue.


A single bad injector can cause a whole system’s worth of problems. When it does fail in older cars, the others are likely to follow suit soon after. Unless you need to fix other things that may be causing your fuel injector to fail (which is usually the case), replacing only one will do little good and cost time and money.

If the car is old and you have the budget, replacing all of them can help you avoid future problems. You just have to find the source of your troubles and act on that or else it will cost you more in the long run.

If you are low on cash, it is best to wait for a little before going ahead with replacement because changing nothing now may mean not having to make another big repair later.

It is a good idea to run a diagnostic scan and see if there is anything else that might be causing the issue before replacing your injector. If you have a code for your bad injector, it’s best to replace only that one instead of the whole system. You may need to do more troubleshooting after this initial fix if the issue does not go away.

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