Last Updated on March 3, 2021
Most vehicles from the 1980’s and newer are equipped with advanced electronic fuel injection engines (replacing the carburetor). A major part of this system is the fuel injector.
While you may never have a problem with your fuel injectors (especially if you regularly use a good fuel injector cleaner), sometimes they get dirty, clogged, or completely fail and need to be replaced.
Below are the most common symptoms of a bad fuel injector and the average cost to replace them (when cracked) or clean them (when clogged).
How a Fuel Injector Works
The basic function of a fuel injector is to supply the engine with fuel. The injector sprays (injects) fuel into the cylinder of the engine through a nozzle so that the internal combustion process can begin.
The fuel must be delivered at the right time, in the right amount, and at the correct pressure, angle, and spray pattern
The Engine Control Unit (ECU) is the central computer or “brain” of any vehicle and manages many individual components, such as the fuel injector. Via various sensors, the ECU makes sure the injector sprays fuel at the right time and in the right amount so the correct air/fuel mixture is created.
A vehicle’s fuel pump pushes gasoline from the tank, through fuel lines, and into the fuel injectors. When the ECU determines fuel is needed, it communicates this to the fuel injector solenoid which then opens to allow the pressurized fuel to spray into the cylinder.
9 Common Bad Fuel Injector Symptoms
If something were to go wrong with one or more of your fuel injectors, then your vehicle’s engine won’t be able to perform the way it’s supposed to.
A faulty fuel injector will either prevent fuel from being sprayed into the engine all together or it will mess up the intervals at which it is supposed to be sprayed. Either way, your vehicle won’t run the way it’s supposed to or even be undriveable.
Below are 9 signs of a bad fuel injector that you can recognize early on. Some of the symptoms of a clogged or dirty fuel injector may be similar so it’s always a good idea to first try running a good fuel injector cleaner through your fuel system before spending the money to replace them.
Alternatively, may need to pay a mechanic to properly clean your fuel injectors or purchase a fuel injector cleaning kit and do it yourself. Either way, you’ll want to take care of the issue soon so no serious damage to your engine occurs.
#1 – Rough Idle or Engine Stalls
Because your vehicle is not getting enough fuel or an uneven supply of fuel, the RPM while idling drops below the optimal level and results in a rough or even violent idle. If the RPM falls too low, the car will actually stall and you will need to restart.
#2 – Engine Vibrates
A faulty fuel injector will cause the corresponding cylinder to not be able to fire. This means that while driving, the engine will vibrate or hiccup after it tries to finish each cycle without fuel.
#3 – Engine Misfires
If the engine does not get enough fuel sprayed into due to a clogged injector, then the engine will misfire as you drive. Your vehicle will struggle to accelerate or there will be a pause after you step on the gas pedal.
Either way, you’ll want to take care of the problem soon or the engine will be susceptible to overheating or other problems that occur when the proper air/fuel mixture is upset.
#4 – Check Engine Light Turns On
The most obvious sign of a problem is when the “Check Engine” light illuminates on your dashboard. Although this could mean a lot of things, a bad fuel injector could be one of them.
Any time an injector delivers less fuel than needed (or more in some cases), the engines efficiency is lowered and can trigger the CEL to come on. Use an OBD2 scanner to confirm the issue.
#5 – Fuel Leak
If your fuel injector is actually broken or cracked from damage or old age, then gasoline will begin to leak out of it. This means the fuel won’t be able to reach the nozzle but instead, it will leak from the body.
If you check the fuel injector, you will notice gasoline on the exterior or on the nearby fuel rail. Often, the leak is coming from the fuel injector seal which deteriorates over time.
#6 – Fuel Odor
This goes along with a fuel leak but when you have gasoline that’s not getting burned due to a damaged injector or one that’s stuck open, you’re going to smell gasoline. Sometimes the issue may be your fuel lines or a faulty sensor telling the ECU to inject more fuel than in necessary.
Either way, you need to find the cause of the gasoline odor and fix it right away before it becomes a big safety hazard.
#7 – Engine Surge
If the fuel injector is spraying too much fuel into the engine cylinder, this will create a surge in the engine causing your acceleration to be much slower. When you drive, you’ll notice that the engine RPM will change noticeable under constant load rather than remaining at a constant RPM.
#8 – Bad Fuel Economy
If the engine is not getting the right amount of fuel it needs for combustion, then it will place more demand on the injector to supply it with additional fuel. This results in poor fuel economy due to the excess fuel that the car’s ECU thinks is needed but is in fact not necessary.
#9 – Failed Emissions Test
Because a broken or leaking fuel injector can cause an uneven or incomplete fuel burn, increased emissions are a result. In some cases, a fuel injector leak can cause the air/fuel mixture to be so rich that it eventually burns out the catalytic converter.
Fuel injectors do not last forever but you can take steps in preserving their lifespan for as long as possible. Many experts recommend that the fuel injectors be cleaned every 30,000 miles or so. That way, the injectors don’t get clogged and prevent fuel from spraying into the cylinder.
Fuel Injector Cleaner
Using a bottle of fuel injector cleaner every now is good preventive maintenance and it’s fairly cheap. Expect to pay about $10-$15 for a bottle of cleaner.
For maintenance, you’d use one bottle right around the time you do a regular oil change but as often as every time you fill your gas tank if the injectors are already showing signs of being clogged.
Related: How to Clean Fuel Injectors
Professional Fuel Injector Cleaning
For more severe cases of dirty or clogged injectors, a more expensive professional cleaning is required. Expect to pay anywhere from $50-$100 for this service.
Some companies even allow you to ship them your dirty injectors where they’ll clean them for around $15-$20 each and then ship them back. They’ll probably do the most thorough job but you’ll obviously have some down time if you need your vehicle.
DIY Fuel Injector Cleaning Kit
Alternatively, part-time or full-time professional mechanics can purchase a fuel injector cleaning kit that will usually pay for itself after a few uses. A good kit (like this OTC set) will include various adapters to allow you to work on most fuel injected vehicles.
Fuel Injector Replacement Cost
Fortunately, most fuel injector issues can be fixed with a professional cleaning or replacement of the O-rings if a leak exists there. But when a fuel injector cracks or breaks, replacement is necessary and it can be expensive.
Although fuel injectors are individual, they are designed to work as part of a team with the other injectors. So if you’re wondering if you can replace just one injector or all, the answer is almost always to replace them ALL.
Depending on your make and model, you can usually expect to pay around $800 to $1,450 for a complete fuel injector replacement. Parts alone are about $600 to $1200 and the labor cost will run about $200 to $250.
There are exceptions of course. Using non-OEM parts can save you some money while certain makes/models of vehicles can run upwards of $2,000 for a replacement. It makes sense to shop around for this type of job.