Problems That Arise From Dirty Fuel Injectors And How To Resolve Them

Your fuel injectors are the heart and soul of your engine’s fuel delivery system, and have been so since the mid-1980s. In this article, we’ll look at what fuel injectors do, and why it is important to keep them as clean as possible.

What Are Fuel Injectors And What Do They Do?

Fuel injectors are basically small nozzles. These nozzles act like water pressure sprayer nozzles, in that they reduce the volume of the tube, thus increasing pressure and flow rate. They work in tandem with a fuel pump. The pump delivers the fuel to the injector, where the pressure builds and allows the nozzle to ‘atomize’ the fuel and deliver it into a combustion chamber.
Fuel injection used to be done by a carburetor, but injectors are more precise at metering the fuel. This innovation has led to better fuel economy (less wasted fuel because of the more precise metering) and more engine power. The amount of fuel that is delivered is calibrated and monitored by the electronic systems within the vehicle.

How Do Fuel Injectors Get Dirty?

Because fuel injectors are the centerpiece of the fuel delivery system, they have a lot of opportunity to get their hands dirty, so to speak. Each time a vehicle shuts down, small droplets of fuel on the outside of the nozzle are exposed to air and evaporate. The evaporating fuel leaves behind small deposits of impurities within the fuel. Over time, these deposits grow (as they are not soluble within the fuel itself and exist as small particles). The buildup can eventually impede the fluidics of the nozzle, causing the fuel to be injected irregularly or at an incorrect rate.

Another way they can get dirty is by being associated with the combustion of fuel. Each cycle of combusted fuel leaves carbon deposits on the pistons and the surfaces of the combustion chambers. This also happens on the exposed nozzle surfaces of the injectors. Once again, as the buildup of carbon grows, the nozzles begin to perform incorrectly.

What Happens When Fuel Injectors Get Dirty?

As stated above, when the nozzles get impeded by deposit buildup, the precise metering of the fuel starts to become imprecise. The most common issues with dirty fuel injectors include the following:

  1. Lower fuel economy, which is related to the imprecise fuel metering by the inhibited nozzle.
  2. Lower power output, which is also related to the metering issues of the fuel. If not enough fuel is getting through the clogged nozzle, there will be less energy derived from the combustion to output to the drive shaft.
  3. Engine knock or ping, which can be caused by an improper air-to-fuel ratio and uneven fuel burn. This occurs because of the uneven amounts of fuel being dispensed by each fuel injector in your engine.
  4. Increased fuel emissions, which is caused by the imprecise metering of fuel (over saturating the chamber).
  5. Hard starting or hard cold starting.
  6. Rough idleing.
  7. Throttle ‘tip-in’ hesitation.

How Do I Know If I Have Dirty Fuel Injectors?

If you have any of the above issues, a good place to start when looking to rectify them is at your fuel injectors. If not, the best way to know is to review the routine maintenance done on your vehicle. Find answers to these questions:

  1. Have the injectors every been professionally cleaned? If so, how long ago? If not, depending on how many miles your vehicle has, it may be time to consider cleaning your injectors. See next question.
  2. How old is the vehicle? Typically, newer vehicles shouldn’t have issues with the injectors. Check your owner’s manual as it will define the maintenance schedule for your fuel injectors. A good rule of thumb would be to professionally clean your fuel injectors every 36 months or 45,000 miles.
  3. Have you ever used a fuel additive fuel injector cleaner formula? If so, this may help to prolong the need for professional fuel injector cleaning, but it likely won’t completely remedy the issues of overdue cleaning. If you are well past cleaning your injectors, fuel additives will have insignificant effect. These should typically be used every oil change or 3,000-5,000 miles.

How Should I Clean My Fuel Injectors?

As discussed above, it depends on how dirty your injectors are. If you are adding some cleaner directly to your fuel, do so every time you change your oil. If you are just now getting around to cleaning your injectors and you’ve never used an additive or had your injectors cleaned and your vehicle has 100,000 miles or more, it is likely time to have them professionally cleaned. Often this will involve removing the injectors, cleaning them (either ultrasonically or with other professional tools), testing them (monitoring the flow and fluidics), replacing any o-rings and lubing them before re-installing them into your engine. Professional jobs shouldn’t cost more than $150 (and usually include an entire fuel system clean). Fuel additive cleaners cost between $4-$20 per treatment.


The fuel injector is the heart of the fuel system. When they work properly and are clean, your engine will hum along at high levels of efficiency and power output. When they get dirty, not so much. It is recommended that you have your injectors cleaned at least every 36 months or 45,000 miles, but this varies depending on the make and model of your car. At a bare minimum, you should keep your injectors deposit free by adding a fuel injector cleaner formula to your gasoline at least every oil change.

We hope that this article was informative. Fuel injectors are usually not considered when performing routine maintenance on your vehicle, and forgetting to do so could case efficiency issues down the road. This site is all about fuel injector cleaners, so feel free to check out some of the reviews on the fuel additive cleaners and other methods for keeping your injectors working in top order. Thanks again for visiting this site and good luck keeping your vehicle’s fuel injectors clean and free of buildup!