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Bad Fuel Injector Symptoms

fuel injector in action
Fuel Injector Spraying Fuel / Credit: Getty / kirilllutz

A fuel injector sprays a carefully measured amount of gasoline into a car’s engine. If fuel injectors aren’t performing properly, your engine won’t either.

Here’s what happens when fuel injectors start to go bad and information about how they work.

What Are Fuel Injectors?

Fuel injectors are a critical component of your vehicle’s fuel delivery system. They are often located toward the top of an engine, spraying a finely calculated amount of gasoline into each combustion chamber. Fuel injectors replaced carburetors, which aren’t as fuel-efficient, in the 1970s and ’80s.

Computer chips monitor modern fuel injectors and are, for the most part, one of the most fail-safe mechanical parts in a car. That doesn’t mean they can’t go bad, however. 

Dirty Fuel Injector
Dirty Fuel Injector / Credit: Getty / MarekUsz

Symptoms of a Bad Fuel Injector

Fuel injectors on modern cars are meant to last the life of the vehicle, though there are always exceptions. Bad fuel injectors can lead to various problems, which, if ignored, could lead to expensive engine repairs. These symptoms include:

  • Car won’t start
  • Car sputters and coughs while idling
  • Engine misfires
  • Engine vibrates noticeably
  • “Check Engine” light is on
  • Lower fuel economy than normal
  • Gasoline smell
  • Tachometer needle spikes upward and then drops again

Not Delivering Enough Fuel

The injectors could be clogged or dirty, so they aren’t delivering enough gasoline to the engine. This leads to what’s commonly called engine “knocking.” Without enough fuel, engine temps soar, and the powertrain could be at risk of total failure. 

Delivering Too Much Fuel

If the injector sprays too much fuel into the combustion chambers, the air/fuel mixture will be rich.

In extreme cases, the engine could experience hydro-locking, which occurs when there is too much liquid in the cylinder, and the piston can’t move. That can be an engine killer.

Fuel Leak

A fuel leak might involve a leaking fuel injector or a leak in another component in the fuel system, like the fuel rail, fuel pump, or fuel lines.

Cost of Fuel Injector Cleaning, Repair, or Replacement

A fuel injector cleaning will cost around $100, depending on the car’s make and model. Resetting the car’s computer to correct the air/fuel mixture is also an inexpensive fix.

However, the more serious the problem, the more expensive the repair. If a simple cleaning or a computer reset doesn’t fix the issue, costlier repairs and replacement parts might be needed. A complicated repair or replacement could range from several hundred dollars to well over a thousand. An engine with more cylinders has more injectors, which can also add to the price.

DIY: Can You Clean, Repair, or Replace Fuel Injectors Yourself?

Simply using a detergent in your fuel (from a Top Tier gasoline, for example) can help clear moderately clogged fuel injectors. However, fuel detergents won’t fix heavily clogged fuel systems. They also won’t help an engine running too rich on gasoline – in that case, the additive could worsen the problem. 

Suppose you’re confident your car isn’t running correctly because of faulty injectors. In that case, the best and most straightforward solution is to find a reputable mechanic to see how extensive the issue might be and let them handle the repair.

Next Steps

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