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9 Signs of a Bad Fuel Injector (and What Causes It to Fail)

Are you having problems with a sputtering, erratic engine? Faulty engines can be caused by a number of problems, but one of the most common is a faulty fuel injection system. You need to identify it correctly, as ignoring the problem can result in much more serious problems down the line. These problems can cost money and even destroy your engine. To determine what you need to look out for, we provide 9 must-know signs of a bad fuel injector. 

1. The Engine Becomes Erratic When Idling

If you halt the vehicle with the engine still running, and it becomes very erratic, it could be a sign of bad fuel injection. This will manifest as shaking and juddering. Severe cases can even see the vehicle stall. 

This happens because the engine is not being supplied with the right amount of fuel when it needs it. The revolutions per minute (RPM) will drop below the amount required, causing the failure.

2. Vibrating Engine

One sign of a bad fuel injector is a lack of response when you push down on the accelerator. This may also manifest as a misfire, as the corresponding cylinder is not getting the fuel it needs. Once the engine is not getting the fuel it requires, it will begin to vibrate in a hiccup type fashion.

This is not strictly a fuel injection problem. It can be a sign of other engine problems. However, it will most likely be a faulty injector.

3. The Engine Light Will Illuminate

If the engine light illuminates, it could be a number of problems, one of which may be the fuel injector. Some of these problems may be quite simple to fix, though some can be major. As a result, you need to address any problems quickly. 

The light is hooked up to your vehicle’s internal computer. Its purpose is to alert you to problems that can be serious, and some of them may be so bad they may not even allow you to travel as far as the mechanic. When you do get to a professional, they will use an OBD2 scanner to read the problem from the computer, then tell you what the situation is. 

A fuel injector may be just one of many problems that could show up. Luckily, it is not one of the most serious. 

4. The Engine Misfires While Driving

Fuel firing is what keeps your engine going, and a lot of this is down to timing. If one of the combustion system components malfunctions, the timing, and frequency of fuel firing are knocked out. The right amount of fuel will not arrive at the correct time and the engine will misfire. 

Worryingly, this will occur while driving. It will make a delay in acceleration, meaning you will not have the power when you need it. This pause in power transferral can be dangerous if you need to move quickly to avoid danger.

5. Fuel Leakages

Aged and damaged fuel injectors can break and crack. This will result in a gasoline leak, and fuel will not be able to get to the nozzle or may reach it in smaller amounts. Instead of the intended outcome, fluid will leak from the engine. 

Fuel will appear on the exterior, close to the fuel rail. The leak will very often come from the fuel injector seal, and this will itself cause more deterioration. You may find fuel puddling on the ground underneath your vehicle. 

6. You Can Smell Fuel

Smelling fuel from within the vehicle is never a good sign. It is a sign that fuel is leaking, and if the smell is making its way into the cabin you may have deterioration elsewhere in the vehicle. The smell of fuel will be even higher when fuel is failing to burn due to a fuel injector that is stuck open or faulty.

A smell of fuel is a huge safety hazard and you must rectify it quickly. The problem can be exasperated by a damaged ECU, which will cause extra fuel to be injected. 

7. Engines Surges

When fuel injectors become clogged, they cause problems because they are not providing enough fuel. However, the opposite can also be a problem. Some fuel injectors may spray too much fuel to the engine, resulting in surges. This surge actually has the effect of slowing down your acceleration.

If you are in motion, your RPM will suddenly increase, and will not stay constant. The combustion system requires a precise air-to-fuel ratio. With more fuel than air, the RPM will increase even if the load is the same. 

8. Decrease in Fuel Economy

If the combustion is not getting the fuel it needs to fire, it will call up more from the injector. The car’s ECU will believe that more is fuel is needed. If you have leakages in the fuel lines in addition, you will soon notice your fuel economy dropping significantly. 

9. A Bad Fuel Injector Will Fail Emissions Tests

When a leaking or broken fuel injector gives uneven or incomplete fuel burns, engine emissions will start to rise. These have serious environmental impacts and you may fail vehicle tests based on emissions alone. 

In some circumstances, the mix of fuel and air can become so rich that the catalytic convertor becomes damaged. The catalytic converter is extremely expensive to replace, much more so than the fuel injector, so ignoring the problem can have bigger financial implications. 

Do Not Leave the Problem

A bad fuel injector needs to be addressed immediately. As well as being an environmental issue, they are dangerous and can cause bigger, more expensive problems later down the line. 

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