Top 10 Symptoms of a Bad Fuel Injector

Modern cars are built with fuel injection engines – in replacement to the use of carburetors. These engines use fuel injectors to “inject” – sprinkle – gasoline/fuel into the engine cylinders for combustion to occur.

However, for pretty different reasons, fuel injectors can get clogged, damaged, or fail completely. A bad fuel injector is a serious issue to get really worried about because it puts the engine at great risk. But how do you know that your car’s fuel injectors are bad?

Some of the most notable symptoms of a bad fuel injector include engine misfiring, vibration, rough idling, increased fuel usage, engine stalling, fuel leaks, inconsistent rpm, illumination of check engine light, etc.

Now, let’s quickly learn more about these bad fuel injector signs!

What is a Fuel Injector?

If this is the first time you’re hearing about fuel injectors, it’s nothing to worry about. A fuel injector is part of the electrical components of the engine, and it plays an important role. It sits together with the fuel pump and fuel filter – they all combine to make up the fuel delivery system.

The fuel delivery system works in a simple way; the fuel pump takes fuel from the tank, pressurizes the fuel to pass through the filter and delivery lines into the injector; the injector then calculatingly sprays the fuel into the cylinders for combustion to occur – to keep the engine running.

When the fuel injector is bad, clogged, or damaged, it’d spray too much fuel, or too little fuel, which would affect combustion, and in turn, affect the engine’s performance. Fuel injectors are controlled by the ECU – it is the ECU that tells the injector how much fuel to spray/sprinkle into the cylinders.

What Causes Fuel Injectors To Go Bad?

The common problem with fuel injectors is “clogging.” When the fuel injectors are clogged, they’d either not spray fuel at all – into the engine, or mess up the spray intervals, which would be detrimental to the engine and its other components.

You may want to ask what clogs the fuel injectors? It’s simple, “dirt.” Fuel injectors get clogged from hydrocarbons, sediment, and other contaminants in the gasoline/fuel that passes through them.

Yes, some fuels and gas do contain fine impurities, which over time, can clog the injectors. Also, the injectors can get clogged by fumes and debris.

Once the injectors are unable to spray sufficient fuels at accurate intervals, the engine would suffer the consequence, and that’s when you start experiencing any of the symptoms below.

Symptoms of a Bad Fuel Injector

1. Misfiring Cylinder/Engine

This is practically the most common symptom of a bad fuel injector. When one or more fuel injectors go bad, the engine cylinders connected to the bad fuel injectors would constantly misfire due to a lack of sufficient fuel supply from the injectors.

Engine misfires affect acceleration and fuel efficiency, as well as cause little vibrations while driving. If you notice that your car is misfiring, one of the things to check and troubleshoot is the fuel injectors.

2. Medium-to-Serious Vibrations

You’d experience serious vibrations when you drive with a bad fuel injector. The vibration happens when the fuel in the cylinders has been utilized and the “bad” injector(s) hasn’t sprayed more fuel yet.

So, the vibrations are due to a lack of sufficient fuel inside the cylinders/combustion chamber.

3. Check Engine Light is Illuminated

Yeah, there are many things that trigger the check engine light to come on – a bad injector is part of those “things.”

When the check engine light comes on, it is important to use an OBII scanner to troubleshoot the actual faulty component that triggered the light to come on.

4. Rough Idling

It is not normal for a car to shake while idling – if this happens, it is due to a faulty engine component, and it could be the fuel injectors.

Once the combustion process is tampered due to fuel insufficiency as a result of a bad fuel injector, it affects a lot of things and can cause the car to shake/vibrate while idling.

Rough idling means that your car shakes, or sputters while waiting in traffic, or when you stop to buy a thing from a roadside shop. If this is allowed to linger, it can lead to more expensive damages in no distant time.

5. Engine Stalling

Engine stalling refers to the unexpected, sudden stop you may experience while driving. Stalling is caused by a wide range of faults in the engine bay but is majorly caused due to lack of sufficient fuel supply to the engine.

That said, a bad fuel injector can cause the engine to stall. While engine stalling is not a major issue to be concerned about, it calls for attention if it happens pretty often – inconsistently.

6. Increased Fuel Usage

If the fuel injector is not clogged but damaged for other reasons, there are chances that the faulty/bad injector would spray more fuel than supposed into the engine, and this would lead to an increase in fuel usage.

When you notice that your car is consuming more fuel than it used to, that’s a sign that you should check the fuel injectors.

Also, it is important to note that when more fuel is sprayed into the combustion chamber, most of the fuel would be wasted – after the required amount has been used for combustion.

7. Inconsistent RPM

A bad fuel injector spraying too much fuel into the engine cylinder would trigger a surge in the engine, which would result in slower acceleration and fluctuating RPM; you’d notice that the RPM gauge is never stable when the car is running with a constant load.

8. Fuel Leaks

If the bad fuel injector is spraying too much fuel, the excesses would get into different parts of the engine and leak out from any possible spot. Also, the fuel injectors can crack due to several reasons, and thus, fuel can leak out from the cracked spots.

You’d notice this by seeing fuel leaks dropping from the engine bay. Of course, this is dangerous and can cause an explosion if a fire is brought close to the place where the leaked fuel touched the ground/floor.

The fuel injector seal deteriorates over time, and it is the major cause of fuel leaks (when it relates to a bad injector).

9. Fuel Smell/Odor

As you may guess, this goes along with the leak. If fuel is leaking out, you’d perceive the odor while driving.

This is a safety hazard, and if you drive a passenger car, your passengers won’t be comfortable sitting inside a car with such a bad smell.

10. Engine Won’t Start At All

Yeah, a bad injector can make a car undrivable. How’s that possible? When the engine is not getting the appropriate amount of fuel it needs to function, over time, the engine components would start to fail, and that can cause the ECU to stop the engine from starting up.

How to Fix a Bad Fuel Injector

If the injector is broken or cracked, sadly, you can’t fix it, you’d have to replace it with a new one. Fuel injectors are not too costly to replace; however, the replacement should be done by a professional or experienced, auto technician to avoid tampering with other critical electrical components that make the engine work.

On the other hand, if the injector is clogged or dirty, you can clean it out yourself following DIY procedures.

Fuel Injector Replacement Cost

You can buy a Fuel Injector Cleaner package; you’d typically find them for $10 – $20 in most auto shops – online and offline. However, if you’d have a professional do the cleaning, expect to pay around $50.

When you confirm the fault is from a bad injector, you can either clean out the injector or replace it.

The average cost of replacing fuel injectors is between $300 and $500 depending on the car model and design. Labor costs can go up to $200 in some mechanic shops.

What More?

Listed and explained in this article are the top 10 symptoms of a bad fuel injector, If you experience any of these signs/symptoms, you should get your engine checked, or troubleshoot with a household auto scanner – such as the OBDII scanner to ascertain if the fault(s) is from a bad fuel injector.