8 Reasons Why Car Runs Rough After Fuel Injector Cleaner & Their Preventions

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Illustration of a car engine with fuel injectors
car runs rough after fuel injector cleaner

A few days ago, a good friend said his car ran rough after fuel injector cleaner. And he was very worried about this issue. So, he asked me to provide help to sort it out. In this case, I thought, why not write about smooth running after cleaning the fuel injection system? It may help many vehicle owners like you!

Typically, a car may run roughly for some inevitable reason. Using excessive or wrong fuel injector cleaners is the most common cause of this issue. Other reasons include:

  • Dislodged debris in the injector.
  • A contaminated fuel system.
  • Issues with the Multec injector.

In this blog, I will discuss all the reasons for a car’s rough running. Also, you will learn about how to start a car after replacing the fuel pump or injectors. Read the discussion to run your vehicle smoothly and get the best driving experience.

Car Runs Rough After Fuel Injector Cleaner – Causes & Preventions

Fuel injector cleaner (or fuel additive) cleans debris and contaminants from car fuel injectors. They are beneficial to distribute or spray fuel evenly to ignite it properly. When the ignition happens correctly, the engine produces accurate power to run the vehicle.

Typical fuel injector cleaners may have detergents and solvents. These ingredients dissolve and remove pollutants from the fuel injectors. However, these being very beneficial, the aftermath may restrict the car from running flawlessly. Well, some reasons initiate this car running problem. They can be:

Dirty or Clogged Fuel Filter

Fuel filters protect the engine by revoking the access of dirt and debris inside. But they can become dirty and clogged over time. Hence, fuel cannot flow properly to the engine in such situations. As a result, you may get a different performance than the regular performance of the engine.

Some symptoms of clogged fuel filters are misfire or rough idle, stalling, and difficulty starting the vehicle. Thus, using a fuel injector cleaner can regain the car’s actual performance. But it will not last long.


Replacing the old, clogged filter will be the best solution. So, check if the filters are healthy even after applying fuel injector cleaner. Many experts suggest replacing the fuel filter after every 20K-30K miles (12). But before that, reading the car manual would be a great idea.

Defective Fuel Injector

Have you been using fuel injector cleaner? Then, there is a chance of a rough start or run, yet you did the right thing. Possibly, you may have replaced the fuel injector. But the new one is not as good as the previous one. So, the new faulty injector is why you feel hesitant to drive the car.

When you choose an aftermarket item, you must ensure that it installs a high fuel pressure. Otherwise, it may stick open and flood the cylinder with fuel. In some cases, excessive fuel drops into the cylinder may cause the car not to start.

Another important thing is that the solenoid of the new injector may not operate well. They may not inject the right quantity of fuel into the cylinder. Hence, your car will not start.


People ask, “How to start a car after changing fuel injectors?” For sure, many car engines require only OEM fuel injectors. Without them, any ordinary injector may fail to manage certain fuel pressures. You should try to use OEM items for better running of the car.

You can test a lousy fuel injector using a multimeter. The injector coil is short-circuited if the device shows OL or minimal resistance. Again, consider the injector is open if the terminal resistance reads infinite resistance.

A good fuel injector will always have a match between the resistance shown on the multimeter and the injector specs.

Wrong or Incompatible Fuel Injector Cleaner

Well, using an incorrect injector cleaner can cause damage to the injectors. You may use them for cleaning, yet they fail to remove the carbon deposits. Moreover, all the cleaners may not be suitable for your engine.


You can prevent car roughness by using expert-recommended products. Many reviews and talks are out there regarding quality and compatible injector cleaners. Also, check what others use who have the same car as yours.

Issues with Multec Injector

Do you know or have ever heard of Multec injectors? These things are available in the cars of General Motors (GM). Again, these injectors have a unique ball design that continuously rotates to remove buildups from the fuel.

Multec injectors let the fuel flow over the injector coils. This process keeps the coil cool and active. When you use chemical-based ordinary cleaners, they can damage the coat on the coils. Gradually, it may harm the injector. As a result, your car will run rough when the injector fails.


If your car has a Multec injector, you should use cleaners specifically made for the vehicle. You can find lots of compatible fuel cleaners online. Another tip would be to check the owner’s manual of your car.

Illustration of a car engine with fuel injectors
car runs rough after fuel injector cleaner

Faulty Fuel Pump

Sometimes, car engines require the replacement of fuel pumps. But a question arises after replacing them, “How to start a car after replacing the fuel pump?” Well, fuel pump changes can also cause rough running after the fuel injector cleaner.

Often, new pumps appear faulty because of their poor technical construction. Again, you may not have securely attached or sealed the pump securely. Even the fuel pressure may not be the same as the earlier one. All this causes the difficulty in driving the car.


First, you should check the fuel pressure. It usually remains 2.5-3.5 bar when fuel is pumped. Then, inspect the pump to see if it draws proper current (2-8 amp) to tally against the factory limits (3).

Ensure that all the newly installed fuel pump connections are properly secured. Besides, transfer the internal sealing O-rings of the old pump to the new one after replacing the pump alone. If you do not do this, the pump will start well but flood the internal sealing interface.

Another suggestion is confirmation of fuel pump wires’ color codes. It helps to avoid incorrect wiring; otherwise, your car won’t start.

Engine Misfiring

The engine misfire is another reason why cars run rough after a fuel injector cleaner. It may happen due to weak spark plugs that cannot ignite the fuel properly. Hence, the misfire of ignition causes cars to stumble and hesitate when you accelerate the car. Though you have cleaned the fuel, engine misfire will cause rough running.


Many car owners may forget this – cleaning the spark plugs. It would be best to keep the plugs clean, especially when taking your car for a long drive. Also, adjust them properly to get consistent performance.

Car Started Problems

Find the car is not starting after using fuel injector cleaner. It may be due to problems with the starter or ignition switch problems. Often, the starter gets damaged over time.


A faulty starter may cause a clicking noise when you turn the key. For the ignition switch, you may hear the same noise while turning the key after turning off the vehicle. So, inspect the components and see if they are in good condition and working well. Otherwise, replacement of those parts may be required.

Blown Fuel Pump Fuse

The fuel pump fuse may go bad when the pump has defects. A defective fuel pump will work more to keep the fuel flow rate and pressure consistent. But it will draw more energy that may heat the fuse faster. And eventually, it will blow off.


Check the fuse after you replace the fuel pump. If it is blown, you must replace it soon to start the vehicle and drive smoothly.

Final thoughts

You know why a car runs rough after fuel injector cleaner well. This article explains all possible reasons for car roughness while driving. So, follow the solutions I have mentioned earlier to avoid any issues.

Always use the proper cleaning product at the recommended quality. Keep everything clean by inspecting them frequently.

I hope you will get the car running smoothly as you expect. Thanks for spending some moments here.

Frequently Asked Questions

There are lots of questions regarding car roughness after fuel injector cleaners. However, some of them are:

  • Can fuel injector cleaners fix rough idle?

If you use the right and compatible cleaner suggested for your car, it may fix rough idle. But you should inspect all other parts of the fuel system thoroughly.

  • Can excessive use of fuel injector cleaner cause problems?

If you overuse cleaner, it can cause rough running in cars. It’s because it can damage the engine parts and fuel system. Eventually, the damage causes leaks and other relevant issues. So, you must apply it according to the car manual or manufacturer recommendations.

  • Can fuel injector cleaners start performing instantly?

Most cleaners are made to work immediately after you apply them. But you may need to wait for significant results.

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