Symptoms of a Bad Fuel Injector

Vehicles use electronic fuel injectors to deliver sufficient fuel to the engine’s combustion chamber. The injectors are advanced, thanks to several years of research and testing aiming to enhance fuel economy in vehicles. The failure of an injector affects the performance of the vehicle. For many drivers, it is hard to identify bad fuel injector symptoms. They end up straining the engine and settling for lower engine power. Here are some signs of a bad fuel injector and approximate repair and replacement costs.

What is a fuel injector?


A fuel injector is a device that delivers fuel to an internal combustion engine. Fuel injection is the process of introducing fuel into the cylinders of an engine where it is combusted. The main purpose of a fuel injector is to deliver precise amounts of fuel at specific times in order to ensure optimal engine performance.

Fuel injectors are designed to operate under extremely high pressures, and as a result, they can be susceptible to wear and tear. Over time, deposits can build up on the injector nozzle, preventing it from opening fully and causing the engine to run lean. If these deposits are not removed, they can eventually lead to engine damage. Fuel injectors must be cleaned on a regular basis to prevent these problems.

How an injector works

Before highlighting the signs of failing or damaged fuel injectors, let’s explore how it works. 

A fuel injector is a critical part of the modern automobile. Its purpose is to deliver a precise amount of fuel to the engine, based on information that it receives from the engine control unit (ECU). The ECU tells the injector how much fuel to deliver, and when to deliver it.

Injectors work by pressurizing fuel to high pressures and then injecting it into the engine at the correct time. This allows for more complete combustion of the fuel, which results in better performance and fuel economy. In addition, injectors help to reduce emissions by delivering a more precise amount of fuel to the engine.

The injector itself is a relatively simple device. It consists of a coil of wire (the solenoid), a plunger, and a nozzle. When the ECU sends a signal to the injector, it energizes the coil of wire, which creates a magnetic field. This field pulls the plunger down, opening the nozzle. Fuel is then forced through the nozzle under high pressure, and into the engine.


The amount of fuel that is injected can be controlled very precisely, based on the needs of the engine. For example, when the engine is cold, it will require more fuel to run properly than when it is warm. The ECU takes this into account and adjusts the injector accordingly.

Signs of a bad injector fuel


Fuel injectors become faulty when the nozzles are clogged or damaged to a point they can’t spray fuel. 

  • Engine stalling and rough idling

A faulty fuel injector causes a poor or erratic fuel supply to the combustion chamber. The engine is deprived of fuel resulting in rough idling. As the situation worsens, the engine stalls since the RPM drops below the desired levels.

  • Engine vibration

A bad fuel injector causes the engine to misfire. It causes the engine to vibrate as it struggles to complete the power cycle with insufficient fuel.

  • Erratic acceleration’

Poor fuel supply means the acceleration will be inconsistent. When the nozzle is clogged, no amount of accelerator pedal pressing will guarantee sufficient fuel supply. It means the vehicle will struggle to accelerate in different terrains.

  • Warning lights on the dashboard

One sign of a failing injector is the appearance of the check engine warning lights on the dashboard. The error signal appears due to several defects. Conducting a scan will assist you to ascertain if it is an injector problem.

  • Fuel leakage around the injector

Extreme injector damage causes cracks on its body. The presence of cracks leads to fuel leakages around the injector.

  • Low fuel economy

A faulty injector is a prime suspect when the car exhibits poor fuel economy. Fuel delivery is uneven. Plenty of fuel is uncombusted. 

  • Surging engine

A bad injector can spray excessive fuel into the combustion chamber. The surged engine affects the quality of acceleration, with drivers experiencing slower acceleration. 

  • Failure to pass emission test

The engine combusts fuel and air at definite ratios. When the injector is bad, it delivers excessive or low fuel amounts. It also sprays the fuel at inappropriate intervals. It means that plenty of fuel remains unburnt. When the vehicle is subjected to an emission test, it will fail as the exhaust gases contain considerable amounts of fuel.

How to fix a dirty fuel injector?

One of the most common issues with fuel injectors is that they can become clogged with dirt and grime over time. If your fuel injector becomes clogged, it can cause a number of problems with your vehicle's engine, including reduced performance, increased fuel consumption, and even engine damage.

Fortunately, there are a few things that you can do to clean your fuel injector and keep it running smoothly. One of the easiest and most effective methods is to use a fuel injector cleaner. These cleaners are designed to dissolve and remove any build-up that may be clogging your injector, restoring it to its original condition.


Simply add the fuel injector cleaner to your fuel tank according to the instructions on the bottle, and then run your engine for a few minutes to allow the cleaner to do its job. You should notice an improvement in your vehicle's performance almost immediately.

If you're looking for a more thorough cleaning, you can remove the fuel injector from your engine and clean it with a brush or other cleaning tool. However, this is a more advanced procedure and should only be attempted if you have some experience working on engines.

No matter which method you choose, cleaning your fuel injector is a simple and effective way to keep your engine running smoothly.

Repair and replacement costs for bad injectors

Fuel injectors have durable lifespans. It is advisable to clean the injector after approximately 30,000 miles of service. Drivers part with $10-$15 to purchase a suitable bottle of injector cleaner. If opting for professional injector cleaning, the driver pays an average of $50-$100.

Replacing damaged injectors is relatively expensive. The cost of an injector and its accessories is between $600 and $1200. Professional mechanics will charge between $200 and $250. 


Driving around with faulty injector results in several engine issues. The vibration, stalling, and misfiring cause discomfort. The low fuel economy means drivers spend more to run their vehicles. Clean the injector immediately if you notice previously discussed symptoms of a bad injector.