How can you identify a clogged injector during testing?

• A. Uneven cylinder firing, rough idle, misfire codes, or decreased fuel economy
• B. Smooth idle and uniform power
• C. No issues
• D. Improved fuel economy

Answer: (A)

A clogged injector disrupts fuel delivery to a cylinder, creating an imbalance in combustion. That imbalance shows up as uneven cylinder firing and a rough idle, because some cylinders get less fuel than others. The engine control unit will typically register misfires and set related diagnostic trouble codes, and overall fuel economy often drops as the engine runs inefficiently.

During testing, these symptoms point toward a clogged injector. You can verify by checking fuel rail pressure and performing a cylinder balance or injector flow test to compare each injector’s output. Inspect the injector spray pattern or use a noid light to confirm operation, and listen for injector clicking with a stethoscope to ensure the injector is actuating. Monitoring fuel trims in a scan tool can also reveal a cylinder that’s starved for fuel. Since a clogged injector leads to rough idle, misfires, and lower fuel economy, this set of signs is the best match.