Six Signs of Fuel Injector Failure

Before we understand the signs of injector failure, it makes sense to understand what a fuel injector is and its function.  At the most basic level, a fuel injector is a device that injects fuel into the engine where it mixes with air and is ignited in the cylinder.

Modern fuel injectors are highly engineered devices that regulate the amount of fuel sprayed based on the engine’s demands.  The engine’s computer sends a signal to the injector that opens and closes a solenoid inside the injector to control the duration and timing of when the injector sprays fuel.  If an injector doesn’t spray for the correct amount of time or if the spray pattern is obstructed it can cause multiple different issues that can be potentially very damaging to your engine and exhaust components.

Six Signs of Injector Failure

Check Engine Light

One of the first signs of an injector malfunction will be from a check engine light on your dash.  The engine control unit, oxygen sensors, and air sensors all play a vital role in controlling the amount of fuel that is needed by the engine.  Sometimes a malfunctioning injector is subtle enough that you may not immediately notice it while driving, but the engine’s computer can sense that something is off.  If an injector in one or more cylinders is not spraying enough fuel, the oxygen sensors in the exhaust can see the combustion gasses and they will tell the ECU (engine control unit) to compensate by spraying more fuel.  At a certain threshold, the computer is going to see that these adjustments are outside of the normal range and will trigger a lean fault.  On the flip side if an injector is spraying too much fuel the ECU can trigger a rich fault because of the excess fuel.  

Poor Engine Performance

Another indication of a potential injector failure would be poor engine performance.  If your engine seems to “bog” down under acceleration or it just doesn’t seem like your car has as much power that could be a sign of an injector fault.  Your engine requires very specific amounts of fuel based on the demands of the driver and if it is getting too much fuel then it can saturate the cylinders and spark plugs causing poor combustion and loss of power.  If there is too little fuel then it can cause engine damaging detonation.

Decreased Fuel Efficiency

If you start to see a decline in fuel economy then you may have an injector problem.  Engines have an ideal ratio of air to fuel called the stoichiometric air-to-fuel ratio.  This ideal ratio allows for the complete combustion of the fuel mixture.  It then follows that if we are burning all of the fuel then we are using it the most efficiently allowing for better mileage.  If we are seeing reduced fuel economy then that is an indication that an injector is spraying more fuel than necessary resulting in a rich condition like we described above.

Rough Idling

A rough idle is another symptom of a failed or failing injector.  If the ECU is unable to reliably control the amount of fuel then it can induce a condition known as a misfire.  All a misfire means is that the combustion inside a cylinder is not behaving how the ECU would normally expect.  Too much fuel can cause a misfire from the saturation of fuel within the cylinder or a fuel-fouled spark plug that can’t ignite as designed.  If there is too little fuel then the cylinder is starved for fuel and the air-to-fuel ratio is high causing the misfire.  

A good way to tell if the injector is spraying too much fuel or is leaking is if you have a misfire at idle and then it goes away when you give it a little more gas pedal to match the higher fuel demand of the engine.

Excessive Smoke

If you are seeing smoke out the tailpipe that is another good sign that your injectors are leaking.  The smoke out the rear of the car is just another indication of incomplete combustion.  What is happening is that your are actually burning off some of that excess fuel in the exhaust resulting in the visible smoke.

Fuel Smell

If you can smell the odor of fuel while you are driving you may have a fuel injector problem.  If too much fuel is being sprayed, or the seal within the injector goes bad it can cause an excessive amount of fuel to end up in the engine.  This oversaturation can be enough that you can actually smell it.  Bad internal injector seals can leak even without the engine running.  When you open your door or turn your key on without starting your fuel pump turns on to prime the fuel system and if an internal injector seal is bad that fuel will leak into the cylinder.  That leaking fuel can make its way into the crankcase mix with your oil and thin it out.  If you pull your dipstick or do an oil change and you smell fuel you have a likely leaking injector problem.

What Are the Consequences of a Faulty Injector

A faulty injector can cause a variety of problems with your vehicle beyond the injector itself.

• Internal bearing damage due to thinning of the oil
• Cylinder wall damage from thin oil causes the oil to be “washed” by the excess fuel removing the critical oil film required
• Damaged and failed catalytic converters from either unburned fuel in the exhaust or from the excessive heat caused by the lack of fuel in a lean condition
• Catastrophic engine failure due to an extreme amount of liquid fuel in a cylinder creates a hyrdolock scenario that can bend piston rods
• Inability to pass emission tests to get your vehicle registered
• Failed spark plugs due to fuel saturation
• Piston damage as a result of damage due to severe detonation from an incorrect air-to-fuel ratio
• Accelerated carbon build up on the back of the cylinder head valves causing poor engine drivability and performance.

What Should I Do?

If you suspect that you have a failed or failing fuel injector the best thing is to bring it into Carlsbad Auto Service and have our certified technicians diagnose your vehicle.  Fuel injectors can be very expensive components and just replacing the part on a suspicion can be a costly mistake.  Our trusted mechanics will get you an accurate diagnosis on what your vehicle needs and repair your car right the first time.  

Give us a call at (760) 729-1155 or schedule online today!