Dirty Fuel Injectors: Symptoms and Cleaning Options

Fuel injectors spray a fine mist of fuel into the engine. When they get dirty or clogged, the spray pattern suffers and the engine doesn't run as it should.

Symptoms of dirty injectors

• Rough idle

• Misfires and shaking

• Hesitation when accelerating

• Worse fuel economy

• Hard starting

• Fuel smell (if an injector is leaking)

• Check engine light with misfire or fuel trim codes

Why injectors get dirty

Over time, deposits from fuel build up on the injector tips, especially when the engine is switched off and residual heat bakes the fuel. Short trips and poor-quality fuel speed this up.

Cleaning options

Fuel additives

A good-quality fuel system cleaner added to the tank can help with light deposits. It's an inexpensive first step, but it won't fix heavily clogged or faulty injectors.

Professional cleaning

For heavier deposits, injectors can be cleaned using equipment that runs cleaning solution through the fuel system, or removed and cleaned on a test bench, which also lets the spray pattern be checked.

Replacement

Injectors that are leaking, stuck or electrically faulty need to be replaced.

Diagnose first

Misfires and rough idle have many possible causes, such as spark plugs, coils and vacuum leaks. A proper diagnosis looks at fuel trims and misfire data to confirm the injectors are actually the problem before spending money on them.

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