How Do I Know If My Fuel Injectors Are Clogged?

by Richard Rowe

As the oldest of electronic fuel injected cars on the road today are more than 50 years old, the problem of clogged injectors has become nearly endemic. This common problem has a number of causes and is fairly easily diagnosed.


The cause of injector clogging is usually metal and dirt debris floating in the fuel stream. Though the system does have a number of filters, they may become perforated over time and allow debris to pass through.


Clogged fuel injectors will often cause a rough, unsteady idle, which may smooth out with gentle application of the throttle.


Clogging can often cause sluggish acceleration and surging under full throttle. In severe cases, the engine may stall under sudden acceleration.


The only way to separate the effects of clogged filters from those of a clogged injectors is misfiring. Injectors usually don't clog in a uniform way, which will cause misfiring of one or more cylinders under hard acceleration.

Bench Testing

The ultimate test is to take your car to a shop that specializes in fuel injection systems and have the injectors flow-tested. This involves removal and testing of the injectors, but allows the mechanic to thoroughly clean them, which is far cheaper than simply buying new ones.

About the Author

Richard Rowe has been writing professionally since 2007, specializing in automotive topics. He has worked as a tractor-trailer driver and mechanic, a rigger at a fire engine factory and as a race-car driver and builder. Rowe studied engineering, philosophy and American literature at Central Florida Community College.

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