Bad Fuel Injector Symptoms

Fuel injectors play a significant role in automobiles, as they deliver the right proportion of fuel to the engine at the right time. In essence, a faulty fuel injector would mean that your car may not have efficient combustion. You may notice many bad fuel injector symptoms, as they go faulty after a while.

What causes fuel injectors to go bad?

There are rarely any issues with fuel injectors, much more if you keep up with good maintenance. Without that, the fuel injectors may go faulty or start becoming clogged. A faulty fuel injector may soon start causing issues that result in serious environmental pollution.

Well, of course, because the engine would not have clean combustion without the supply of fuel at the right time. Kindly note that the fuel supply to the engine must also come in the right fuel pressure, spray pattern, and angle.

The injectors work alongside the fuel filter and pump to ensure that the engine gets the correct fuel and air mixture. Only after the adequate supply of the fuel and air mixture can the car’s combustion chamber ignite and power the engine. Also, you may notice that the car starts but won’t stay running with this fuel supply issue.

how to clean fuel injectors

Bad Fuel Injector Symptoms

Clean fuel injectors spray the right amount of fuel to the engine’s cylinder and do so at the right time. The fuel gets supplied with the aid of the nozzle and ensures a smooth and clean combustion process. Hence the need for regular cleaning with a suitable fuel injector cleaner.

The fuel should also come with the correct air/fuel mixture, which becomes possible with the sensors from the car’s Engine Control Unit. When one or more fuel injectors go faulty, the car’s engine won’t perform effectively. In extreme cases, the engine won’t start, and that can be pretty frustrating.

A swift fix of the fuel injectors would be right, and for that, you need to take note of the common signs that tell you that the fuel injectors have some faults. What happens when fuel injectors go bad? Here are some common symptoms:

Engine Vibration

The engine would start vibrating in a bid for the engine to complete a functioning cycle with little or no fuel entering the manifold intake. Why does this occur? The faulty fuel injector would not inject fuel via the nozzle, which caused its corresponding cylinder not to fire.

Check Engine Light Turns On

One of the common symptoms of bad fuel injectors is the check engine light turning on. Only when there is a problem with your engine can you see the light illuminating your car’s dashboard.

So, when you notice such, you should endeavor to check the fuel injectors. The engine’s efficiency often reduces with fewer amounts of fuel delivered by a faulty fuel injector. Such a situation can trigger the Check Engine light to turn on. Further probing using the OBD2 scanner can help you get a quick diagnosis.

Engine Misfires

Ever noticed an engine misfire? It may seem strange and appear to be one of the frustrating things for car owners to handle. Nevertheless, bad or dirty injectors can cause an engine to misfire; because of the little or no provision of fuel in the car’s combustion chamber.

In most cases, this results from issues with the fuel injectors, creating an imbalance in the fuel and air mixture. Such a case can start sending some serious vibrations via the vehicle.

Fuel Smell

While driving with a bad fuel injector, you may soon start perceiving that offensive fuel odor. This odor often comes as one of the leaking fuel injector symptoms. Nevertheless, with the gasoline not getting burned in the combustion chamber, you still have to deal with such a fuel smell.

It may also be due to a misdiagnosis of the ECU receiving sensors that instruct the system to inject more fuel. When the injected fuel appears more than what is needed, the fuel smell lingers in the car.

Fuel Leakage

When the fuel injector is broken or starts having some cracks due to long use, the gasoline may soon start leaking. Leaky fuel injectors may prevent fuel from reaching the injector’s nozzle. As such, there would be no fuel provision for the engine to function.

The leaks may also be due to the fuel injector seal that starts deteriorating with time. Most fuel leaks through, making fuel noticeable on the fuel rail that lies close by. Perhaps you may want to check your fuel injectors when you notice this symptom.

Poor Fuel Economy

There may be some drop in the fuel economy with the fuel injectors having some faults. This issue often results from the inadequate supply of fuel to the combustion chamber. In essence, the less fuel supplied to the engine, the lesser the fuel economy of your car.

Engine Stalls

Do you find your engine stalling randomly without any visible cause? Well, that could be due to faulty fuel injectors. The ECU often stops the engine when sufficient fuel doesn’t reach the combustion chamber from the injectors. Hence, a possible reason for the engine stall.

Rough Engine Idle

One of the bad fuel injector symptoms for BMW and other car engines is the drop in RPM levels while idling. That bad fuel injector sound should tell you that the injectors may not provide the required amount of fuel needed for the engine’s functionality.

Engine Surge

This problem is pretty common when the fuel injectors supply more fuel than needed, and soon you would start some changes in your RPM with constant load. In essence, you won’t get to see that constant RPM under such circumstances.

When there is excessive fuel spray into the corresponding cylinders of each fuel injector, this visible surge leads to a “slow” acceleration.

Note: The fuel from the tank moves through the fuel line from the fuel pump and enters the fuel injectors. So, a bad fuel pump would mean that the fuel injectors would not get sufficient fuel. Nevertheless, you may notice this issue quickly if you conduct a regular fuel induction service for the car.

How to Diagnose, Test and Clean Dirty, Clogged or Bad Fuel Injectors YouTube

Frequently Asked Questions (FAQs)

Q: Can you drive with a bad fuel injector?

Driving a car with a faulty fuel injector can cause some further issues. When you drive, you may soon start noticing some vibrations at each traffic stop, and the engine may soon start stalling. Also, this may cost you more on refilling your fuel tank, as leaky fuel injectors would lead to loss of fuel.

There would be serious smoke emissions from the car’s tailpipe, causing some serious pollution in the environment. With some associated engine problems, it would be best if you try to fix your faulty fuel injectors before you resume driving your car.

Q: Will a bad fuel injector throw a code?

Various fault codes appear due to a faulty fuel injector. These codes often range from misfire to lean codes. You may soon start seeing codes like P0300 and P0308. This diagnosis is thanks to the OBD2 scanner.

When there is an issue with the car’s engine, you would often find the engine check light. With a faulty fuel injector, one sign you would notice is the light on your dashboard. One way of understanding the real diagnosis is knowing the possible causes of the issue.

Q: Do fuel injector cleaners work?

You can prevent some fuel injector problems with thorough cleaning practices. Using a fuel injector cleaner would be pretty helpful. Most of the best options in the market contain Polyetheramine, Polyisobutene, and Polyisbutlylene amine.

These ingredients are effective cleaning agents that would remove dirt from the fuel injectors. Some cleaners also contain alcohol for excellent water removal from the injectors. However, these alcohol-containing cleaners may cause damage to some parts of the fuel system.

Q: Will fuel injector cleaner fix a misfire?

Dirty and clogged fuel injectors often result in various issues like an engine misfire. In most cases, car owners get lucky when cleaning their fuel injectors, as they notice the engine misfiring stops after the fuel injector becomes unclogged.

Nevertheless, if the engine misfire is due to bad spark plug wires, the fuel injector cleaner would have no effect. So, you may need to fix that issue yourself or with the aid of an expert before it goes away.

Q: What happens if you put in excessive fuel injector cleaner?

There may be some issues with your fuel injectors if you start putting in too many cleaners. Undoubtedly, constant cleaning of the fuel injectors may ensure that it functions optimally and supplies fuel when needed.

Nevertheless, you may start noticing some damage on your fuel tank lining with too many fuel injector cleaners. Thus, it is crucial to learn how to clean fuel injectors and add the required amount of cleaners when you do so.

Final Words

Fuel injectors are an important part of the car that helps supply the required amount of fuel when needed. When the fuel injectors get clogged due to dirt or start wearing out with constant use, the corresponding cylinders would not get sufficient fuel spray.

With that, the engine combustion chambers do not get sufficient fuel needed to ignition the car. Some more severe damages may result due to this problem. It is crucial to note the various bad fuel injector symptoms and fix the issue quickly. This article provides a glimpse of such signs that signifies a faulty fuel injector.


Hi There, I am R. Hasan Tito, a mechanic, and owner of this website. My friend and I created this website to share our knowledge, expertise, and experience with our fellow mechanics' community and car users. I am a specialist and certified automotive mechanic (Both Heavy Commercial and Private Cars). I have been working as a mechanic for over fifteen years. I worked for a long time at Global Rebound Automotive companies (Toyota, TATA, BMW, Nissan, TVs, and Others ) as a Mechanic and Mechanics Supervisor.

Recent Posts