Clogged or Dirty Fuel Injectors: Symptoms, Causes, and Solutions

You know how important your engine is to the overall performance of your vehicle, and the fuel injection system plays a big part in it all. But when those fuel injectors get dirty, things can start to go wrong.

dirty fuel injectors

Here at AllCarFix, we’ve seen it all. I’ve witnessed clogged injectors cause rough idling, dirty injectors lead to decreased fuel efficiency, and even seen engine misfires due to faulty fuel injectors.

But don’t worry, with a little know-how, you can keep your fuel injectors in tip-top shape. In this article, we’ll go over all the signs of dirty fuel injectors, why they clog up in the first place, and how you can clean them.

Let’s get your engine running smoothly again!

Symptoms of a Clogged or Dirty Fuel Injectors

Recognizing the symptoms of dirty fuel injectors can help you diagnose the problem early and prevent it from becoming a more significant issue. How do I know if one of my fuel injectors went bad? You asked.

Well, here are the most common symptoms:

  1. Check Engine Light: The first is the check engine light being triggered. If your scanner threw a P0200 or its variation (P0201, P0202, etc.) code, there must be a problem with one of your fuel injectors.
  2. Dirty Exhaust Emissions: A bad fuel injector can also lead to dirty exhaust emissions. An insufficient or abundant fuel supply can enhance the production of unwanted gases during combustion.
  3. Poor Performance and Rough Idling: Dirt, grime, and soot can accumulate in the engine’s fuel injectors, leading to an air-fuel mixture imbalance. When this happens, it may result in poor performance and rough idling.
  4. Inconsistent Gas Mileage: The fuel injector may spray fuel inefficiently when it becomes dirty or clogged leading to an air-fuel mixture imbalance and decreased power output. This can result in reduced gas mileage.
  5. Misfiring engine: On turbocharged engines, a clogged or dirty fuel injector can cause a detonation that leads to a misfiring engine.
  6. Fuel Leak: Old age or damage can cause fuel injectors to crack or break, leading to fuel leaks.

How to Diagnose Bad Fuel Injectors

If you experience one of the symptoms above, you may have a bad fuel injector. But the truth is, most car problems and issues share the same symptoms. So in this section, let’s accurately diagnose if fuel injectors are the culprit.

Although diagnosing bad fuel injectors can be a process, it can be done with the right tools and techniques; let us walk through the steps.

Step 1. First, take a look at the fuel injectors. We always recommend popping them out and giving them a good visual inspection to see if there’s any damage or wear. Sometimes, you can see the problem right away.

Step 2. If that doesn’t do the trick, it’s time to run a cylinder balance test with an electronic injector pulse tester. This test will help determine if disabling a fuel injector changes the engine’s idle quality or performance. It’s cool to see the difference for yourself.

Watch this helpful video demonstration from 737mechanic on how to test fuel injector using a balance test:

Step 3. Next, use an OBD code reader to see if the engine control unit (ECU) has logged any errors. This is one of my favorite tools because it saves so much time. Here is a table of the most common OBD 2 codes that indicates problem with the fuel injection system:

OBD CodeProblematic Part or SystemDescription
P0261Fuel Injector“Cylinder 1 Injector Circuit Low”
P0262Fuel Injector“Cylinder 1 Injector Circuit High”
P0263Fuel Injector“Cylinder 1 Contribution/Balance Fault”
P0264Fuel Injector“Cylinder 2 Injector Circuit Low”
P0200Injector Circuit“P0200 is a generic OBD-II diagnostic trouble code in reference with the injector circuit.”
P2146Fuel Injector“Fuel Injector Group A Supply Voltage Circuit/Open”
Most common OBD 2 codes on faulty fuel injection system

These codes generally indicate issues with either fuel injectors, or the circuits that control them. Depending on the code, the problematic part could be a faulty fuel injector, an injector circuit that is malfunctioning, or a supply voltage circuit that is open.

It’s always best to consult with a professional mechanic to get a more accurate diagnosis of the issue, especially if you’re not sure what the code means.

Step 4. And finally, a friend or helper can turn the key to crank the engine for 3-5 seconds at a time while you observe the fuel injectors. Please make sure they spray fuel as the engine turns. This step is crucial and can reveal a lot about the health of your fuel injectors.

Read more: 3 Simple DIY Methods How To Check For Leaking Fuel Injectors

Causes of Dirty Fuel Injectors

Fuel injectors can become dirty due to several reasons, including the following:

  1. The use of low-quality fuel: Using low-quality fuel can cause deposits to form in the injectors, leading to clogging.
  2. Age of the injectors: Over time, fuel injectors can become dirty due to the accumulation of debris and contaminants.
  3. Engine gunk and carbon: Hydrocarbons and additives that are part of today’s fuels, together with engine gunk and carbon, can cause injectors to become restricted.

Read more: The Truth About SeaFoam – Can it Hurt Your Engine?

Cleaning Dirty Fuel Injectors

Now that you have fully understand the symptoms of dirty or clogged fuel injectors and how to diagnose them, let’s talk about cleaning it. There are two ways to clean dirty fuel injectors: professional cleaning and DIY cleaning.

Professional Cleaning

Now let’s talk about fuel injector cleaning costs. A professional fuel injector cleaning in 2023 can range anywhere from $15 to $150 with an average cost around $100.

However, the cost of cleaning will depend on various factors, such as the level of cleaning required and the make and model of the vehicle.

If you’re looking to save a little money, you can do a simple fuel injector cleaning yourself at home for as little as $10. But if you want your car’s fuel injectors to be cleaned to a professional level, then it may be worth paying a little extra for a full-service cleaning at a local auto-service, which can cost between $60 and $100.

How to Clean Dirty Fuel Injectors

Fuel injectors are prone to dirt and grime accumulation over time, which can impact your vehicle’s performance. Dirty fuel injectors can lead to poor performance, rough idling, and inconsistent gas mileage.

Fortunately, cleaning dirty fuel injectors is a relatively simple process that you can do yourself with the right tools.

Here are the steps to clean your vehicle’s fuel injectors:

  1. Find the Fuel Rail Test Port: You will connect the fuel injector cleaning kit. Please consult your vehicle’s owner or maintenance manual to find it on your vehicle.
  2. Connect the Fuel Injector Cleaning Kit: Connect the cleaning kit to the fuel rail test port.
  3. Run the Cleaning Solution: Turn on the engine and allow it to run for a few minutes while the cleaning solution runs through the fuel injectors.
  4. Disconnect the Cleaning Kit: Turn off the engine and disconnect the cleaning kit from the fuel rail test port.
  5. Start the Engine: Let it run for a few minutes to check if the cleaning has been effective.

If you are uncomfortable performing these steps yourself, you can take your vehicle to a professional mechanic who can clean your fuel injectors.

Alternatives to Cleaning Fuel Injectors

In addition to cleaning your fuel injectors yourself or by a professional, bottled synthetic injector cleaning products are available on the market.

One such product is Prestone, which sells a bottled synthetic injector cleaning product. This product is advertised as combining synthetic detergent technology with the benefit of octane enhancement. It is said to improve acceleration by cleaning dirty fuel injectors.

Using a Fuel Injector Cleaning Solution

Another option is to use a fuel injector cleaning solution. Prestone sells a bottled synthetic injector cleaning product to clean dirty fuel injectors and improve acceleration. This product combines synthetic detergent technology with the benefit of octane enhancement. [2].

Using a Fuel Injector Cleaning Kit

Using a fuel injector cleaning kit, you can also clean the fuel injectors yourself. A fuel injector cleaning kit typically includes a cleaning solution and an adapter that connects to your vehicle’s fuel rail test port. To use the kit, you need to follow these steps:

  1. Find the Fuel Rail Test Port – The fuel injector cleaning kit connects to the fuel rail test port. Consult your vehicle’s owner or maintenance manual to locate your vehicle’s test port.
  2. Connect the Cleaning Solution – Connect the cleaning solution to the fuel rail test port.
  3. Start the Engine – Let it run for about 5 minutes to allow the cleaning solution to circulate through the fuel injectors.
  4. Repeat the Process – Repeat the process if necessary until the fuel injectors are clean.


Bad (faulty, dirty, clogged, leaking fuel injectors) fuel injectors can cause a variety of problems for your vehicle, including poor performance, rough idling, and inconsistent gas mileage. Keeping your fuel injectors clean can improve fuel efficiency, increase horsepower, and extend the life of your vehicle.

Before replacing fuel injectors, you must consider cleaning them first.

Cleaning your fuel injectors can be done professionally using a cleaning solution or a fuel injector cleaning kit. Cleaning your fuel injectors will help ensure your vehicle runs smoothly and efficiently regardless of your chosen method.

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