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.

How an injector works

Before highlighting the signs of failing or damaged fuel injectors, let’s explore how it works. The electronic fuel injector depends on the electronic control unit for its operation. It picks signals from the sensors to open and close the injector nozzles, delivering appropriate amounts of fuel depending on the driving conditions. 

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.

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.