9 warning signs of a faulty fuel injector: Explained


Posted by: Joshua-Philip Okeafor

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A fuel injector is a very vital part of most modern internal combustion engines? What if this fails? Do you know the signs that it is failing? Read more!

Newer vehicles built from the 1980s to date come with Advanced Electronic Fuel Injection Engines. These engines have successfully replaced the engines powered by carburetors. The fuel injector is an essential part of this new fuel injector system. Like any system, fuel injector parts or components can go bad.   Do you know the warning signs of a faulty fuel injector?


Fuel injectors are so vital to modern automobiles

What is a fuel injector and what does it do?

Of course, there is always the carburetor versus fuel injector, which is better, debate. However, for a modern car engine, a fuel injector is seen as an essential part of its smooth running.

Without going in-depth into the fuel injector working principle, it is possible to briefly answer the questions what is a fuel injector and why is it important? We can say that the main fuel injector function is to deliver fuel at the exact time it is needed to the internal combustion engine, and thus ensure the effectiveness of combustion.

It is very essential and important for all drivers to be able to recognize a faulty fuel injector and work on it quickly before it affects the function of the car engine at large. 

When fuel injectors develop faults, this automatically affects the fuel injection, performance as well as causes breakdowns for the cars. When they become damaged, they probably have become clogged with sediments, dust, or other debris. They also might have been altered by factors like electrical and mechanical determinants.  When we say a fuel injector is clogged, it means that the junk in the injector has built up to a point where it refuses fuel to flow through. 

Having said this, let’s quickly take a look at some indicators of a faulty injector you should see. 

1.  Check engine warning light

When a fuel injector becomes faulty, the most obvious occurring sign is the check engine light which is always found on the dashboard of your car. When the engine warning light pops up, there could be a number of reasons for this.

Part of what it is telling you could be that the fuel injector is either hyper-performing or under-performing. The ECU (Engine Control Unit) is the brain of any vehicle. It manages all the individual components and ensures fuel injectors supply and spray fuel correctly at the right time and in appropriate quantities dispatched to ensure accurate air/fuel mixture. This engine computer passes a message across through the Check Engine light when it notices abnormality in the performance of the fuel injector. 

The engine efficiency will decrease at this point and push the CEL (Check Engine Light) technology) to pop up. An OBD2 scanner can be used to confirm if it is the fuel injector or not.  It is, however, pertinent to know that while the Engine Warning Light is not an automatic indicator of a faulty fuel injector, it could be one of the reasons. So, to be on a safer side, either open the bonnet to check the cause for it or see your mechanic. 


When check engine light comes on, it means trouble!

2.  Engine misfiring or slow acceleration response

When your accelerator pedal responds slowly to your foot pressure or your engine fails to ignite properly, you might be looking at a faulty fuel injector (the nozzle being blocked or clogged up). When the fuel injector refuses to deliver its correct quantity to the engine at the right time, the fuel-air mix operation or carburetion, which happens in the combustion chamber is thrown off. This single action can make the engine to misfire and can cause the acceleration level to drop.  

The engine has a strong likelihood to overheat, due to the upset caused by the air/fuel mixture. This can lead to accidents through failure in performance while the car is in motion. That is why it is of utmost importance to keep our fuel injectors safe by undertaking fuel injector cleaning. Fuel injector oil or Fuel Injector Lubricant may or may not be necessary depending on where it is a direct or indirect injector system. Your mechanic will decide.

3.  Change in car idle noise

When the noise from your idling car begins to sound strange, the fuel injector pump might not be drawing and supplying fuel as it should. For your car to work optimally, fuel injector pressure needs to be constant. These sounds might well be indicators of other faults in the car but this is also one of the commonest signs of a clogged fuel injector or damaged fuel injector kit. 

4.  When your engine stalls

When your engine decides to cut out or just stall without being told to, it might be the fuel injector not supplying enough fuel to the engine. When the proper amount of fuel designed to reach the combustion chamber does not get there, the ECU sends a signal to the engine to stop, which causes an engine stall. In this situation, the RPM when idling drops below its optimal level and that might make its idle output either rough or violent. When this RPM drops too low, the car might stall and you need to start all over.


Haha, not great when the car quits on you, right? 

5.   Fuel leaks

When driving, if you begin to smell fuel in the cabin as well as other signals said above, this is one of the possible fuel injector leak symptoms. It means something is definitely wrong as there is a strong possibility of a fuel leak. Fuel leaks can result from the meeting point of the injector, and the fuel injector seal (which eventually deteriorates), or when the injector has become old or badly managed. 

The fuel at this point isn’t able to reach the fuel injector nozzle because of the cracks or breaks on the exterior of the injector, and so leaks from the body. If the injector being damaged is the cause of this leak, the fuel will be seen on its body and cause a smell. You are supposed to check everything properly or have the mechanic do so.


Leaking fuel injector system, a big issue you should deal with

6.  Poor fuel economy

The fuel economy drops when the fuel injector is faulty. At this point, the ECU is asking for fuel from the injector for the combustion chamber but the injector is failing in its duties. The thing is, the more fuel supplied to the engine, the lower the fuel efficiency or economy but the lesser the supply of fuel to the engine, the higher the fuel economy. Every driver needs to understand this to avoid accidents caused by faulty fuel injectors.

7.  Vibrating engine

When you work with a faulty fuel injector, it might make corresponding cylinders to lose the ability to fire. The implication is that the engine vibrates or hiccups after struggling to finish a cycle without an adequate supply of fuel. Fuel injector flow testing may be able to define the problem. This can be achieved by a simple fuel injector flow calculator or other fuel injector testing methods.


Fuel injector problems can lead to engines vibrating

8.  Emissions test fail

A broken and leaking fuel injector can cause uneven fuel burn; which results in increased emissions. When the fuel injection leak causes a rich air/fuel mixture in some cases, it might burn the catalytic converter out. This is one of the fuel injector symptoms you must watch for.

9. Temperature

A dead injector tends to make the engine begin and operate itself when cold instead of when warm. When injectors or even the filter baskets become clogged, there is no amount of induced injector cleaner that will do the trick. You just need to remove it yourself from the engine or seek the help of a mechanic. Afterward, you take it to a professional fuel injector cleaner to clean it up. A fuel injector filter works to mitigate these fuel injector problems. It is important to keep your fuel injector clean using simple methods.

This video will show you a quick fuel injector test:

Testing Fuel Injectors quickly


We have established your engine needs the fuel supplied by the fuel injector to function. This is true of petrol or alternative fuels. A damaged fuel injector equals no functional engine and no movement at all from your car.  Then you will need the expensive services of a mechanic using a fuel injector kit.

No matter the fuel injector types in your vehicles, hopefully, these warning signs of a faulty fuel injector will make it easy for you to spot the fuel injector issues in plenty of time to save yourself a breakdown.

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Joshua-Philip Okeafor

Joshua-Philip Okeafor

Car buying & selling

Joshua, or KK as friends call him, is a Filmmaker, Writer and Director. A Christian, Joshua is a product of Nigeria’s foremost film school, the National Film Institute, Jos, where he majored in Writing/Directing. Joshua began his writing career at age 18 when an older brother gave him a four page outline of a children novel. Joshua intends to keep writing and directing. His screen name is sometimes Joshua Kalu Ephraim (Writing), and sometimes Joshua KK (directing).

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