How to Tell if the Fuel Injector is Faulty?
3 Answers
Signs of a faulty fuel injector: 1. Black smoke from the exhaust pipe; 2. Uneven operation of cylinders; 3. Noticeable engine vibration; 4. Decreased engine power; 5. Weak vehicle performance; 6. Unstable idle speed; 7. Increased fuel consumption, poor acceleration, difficulty starting, excessive vehicle emissions, and in severe cases, engine damage. The fuel injector is essentially an electromagnetic valve, with its nozzle facing the intake valve and its tail connected to the fuel distribution pipe. When the engine ECU sends a fuel injection command in the form of an electrical pulse, the electromagnetic coil inside the injector is energized to create a magnetic field, opening the injection hole to spray fuel into the engine. When the ECU's injection command ends, the injection hole closes under the action of the reset spring, and the injection process stops immediately. The duration of the injection hole opening (i.e., the amount of fuel injected) is determined by the width of the electrical pulse sent by the ECU.
I experienced a fuel injector failure last year, and the symptoms were unmistakable. When starting the car in the morning, the engine shook violently like a sieve, and black smoke billowed from the exhaust pipe. While driving, pressing the accelerator felt sluggish—the tachometer needle fluctuated up and down without gaining speed. Fuel consumption suddenly skyrocketed; normally, a full tank would last 500 kilometers, but that time it only managed 300. The scariest part was when the check engine light suddenly turned yellow. At the repair shop, a diagnostic scan confirmed that the third cylinder's fuel injector was clogged. The mechanic mentioned that ethanol-blended gasoline tends to cause carbon buildup and recommended adding a bottle of fuel system cleaner every 20,000 kilometers to prevent clogging.
As a veteran driver with 20 years of experience, I rely on these three practical methods to diagnose fuel injector issues. The most accurate is listening during cold starts: if the engine coughs and sputters accompanied by metallic knocking sounds, it's likely due to poor fuel spray. At idle, feel the exhaust pipe with your hand—it should be dry; if there's black, sticky oil residue, it indicates incomplete combustion. Finally, test acceleration performance by revving to 3000 RPM in neutral and suddenly releasing the throttle—if the RPM needle stutters noticeably during drop, something's wrong. Don’t wait until it completely fails to fix it. Always choose fuel from reputable gas stations, as poor-quality gasoline is particularly harmful to fuel injectors.
