Clogged fuel injectors

There are many ways clogging can affect the injectors. Click to enlarge.

The importance of cleaning clogged fuel injectors cannot be overstated. But how to tell if your fuel injectors are clogged? Or faulty?

Engine trouble is rarely easily identified, but there are symptoms for every issue, symptoms that everyone can learn to notice.

So, in this article, I’ll try my best to help you understand how the various issues caused by dirty injectors present themselves and how you can learn to notice them in a timely manner.

Dirty, clogged, blocked, leaking or generally faulty fuel injectors have the following symptoms:


  • Engine stutter, hesitation, stumbling – without the proper air/fuel mixture, the combustion inside the cylinders is impeded.
  • Engine misfire – poor air/fuel mixture in the cylinders can cause an incomplete combustion event.  The cylinder can miss a stroke, causing immediate engine power loss and a noticeable sound effect. When this becomes severe enough, the driver will feel a jerking action from the engine and/or powertrain.
  • Performance loss – the engine needs sufficient fuel for a proper, strong combustion. If combustion is impeded, engine power suffers.
  • Rough idling/engine stalling – uneven supply of fuel during idling can cause RPM to fall too low and result in stalling.

For example have a listen to this bad fuel injector sound:



In addition to performance issues, you will also have to deal with:

  • Failing emission tests – the drop in fuel combustion efficiency causes incomplete or uneven fuel burn, increasing emissions.
  • Increased Fuel consumption – when fuel combustion efficiency is negatively affected, you will often need to burn more fuel to achieve the desired levels of performance.
clogged fuel injector symptoms

Liquid fuel injector cleaners are easy to use

Blocked diesel injector symptoms are similar. And in many cases can lead to an easier diagnosis of the issue, as the lack of spark plugs in diesel engines mean that there’s one less potential cause for the problems.

When you notice any of these clogged fuel injector symptoms with any of your vehicles or other mechanical equipment using fuel injected engines, it’s definitely a good idea to look into some injector cleaning products.

However, once again it pays to emphasize the value of prevention. Proper maintenance schedule that includes regular use of injector cleaners (either liquid additives or manual cleaning kits) can go a long way in keeping your vehicles operating smoothly and reducing any repair bills down the road.


That’s because when it comes to fuel injector clogging, it is not a case of IF, it is a case of WHEN.

Meaning, that sooner or later the fuel injectors on your fuel injection engine will get dirty and will get clogged to some extent. This is especially true for machines that regularly operate for short periods of time (like driving short distances in the city, or using farm equipment) as multiple engine ignitions and shut offs will exacerbate the clogging.

It’s just one of those unavoidable things that comes with the territory of operating modern, fuel injected engines. Unless of-course you make sure to maintain your vehicle properly.

Bike Engine maintenance

Perfect maintenance can be a huge undertaking. Photo by Aaron Huber on Unsplash

And while getting your injectors cleaned by a professional isn’t overly expensive (ranging from $50-100), having them changed because of irreparable damage can cost A LOT more. I don’t want to alarm you, but fuel injector replacement cost can reach well into the hundreds of dollars.

Though you can always choose to get your hands dirty and deal with the issues yourself, in which case check out this article: Fuel Injector cleaning – how to clean Fuel Injectors?

Why are fuel injector issues such as clogging or leaking so common?

Well, to put it simply – Fuel injectors have the important job of dispersing fuel into the engine at the exact angle and quantity needed for the engine to operate optimally. And because there are several fuel injector nozzles that must evenly disperse the fuel, it only takes one dirty nozzle to influence engine performance. So any risk to the injector is effectively multiplied by the number of injectors in the engine.

And despite the issues dirty injectors can cause, early symptoms aren’t always noticeable because modern engines have internal sensors and computers that can adjust the fuel mixture to compensate for minor errors. That in turn can cause the beginning phases of clogging or leaking to go unnoticed.


It is also worth mentioning that vehicles that use turbocharged engines are at a risk for uncontrolled, engine damaging detonations. This can happen due to an overly lean condition caused by the dirty injector.

Turbocharged engines that reach high RPM’s require a much more accurate fuel dispersion rate than other types of engines. If the fuel injectors are dirty of clogged or otherwise out of balance, the risk for engine damage can be very high.

It definitely makes sense to be proactive about this to save yourself a lot of money and headache in the long term.  Fuel injector problems can be a serious matter.

This is not to say that detonation cannot become an issue on other automobiles as well, as it definitely can. However, for most regular fuel injected engines, detonation is more often caused by using low-octane gasoline. While liquid cleaners aren’t always designed for this, many products also act as fuel octane boosters, raising the octane rating of the gasoline and thus helping to reduce dangerous detonations.

Here’s a very good video that explains the entire concept of detonation and octane ratings in great, easy to understand detail:



At this point it is also fair to note, that all of the symptoms mentioned in this article can also refer non-injector related issues. Engines are complex pieces of machinery and there are usually several parts in the system that can produce similar symptoms when failing. So what you might take for a bad fuel injector sound, can at times refer to bad spark plugs for example.

If you want to be 100% certain what the issues are, a visit to a professional mechanic is always a good idea. However, the reason why I recommend fuel injector cleaners first, is because of their low cost and ease of use.

Adding some liquid cleaner to the fuel supply is a safe, time saving method to try before sending your car to the shop.

Let’s re-cap with this simple Infographic we’ve prepared for you:

Clogged Fuel Injector Symptoms - an infographic

Click to Enlarge


So, next time you are driving your car, motorcycle, or operating any fuel injected piece of machinery, remember to keep an eye out for these symptoms that might indicate dirty, leaking or clogged fuel injectors. Or better yet, avoid them in the first place by using cleaners regularly!

And to see whether a cleaner has helped your car, try out our handy fuel consumption calculator! Check your mileage and keep track of how it changes.

– Jack


More Content at our site: