Check for engine misfires, rough idle, hard starting, poor fuel economy, or fuel smell
Listen for injector clicking with a mechanic’s stethoscope or long screwdriver
Use an OBD2 scanner to check for misfire codes and fuel trim issues
Inspect injector wiring, connectors, and fuel rail for damage or leaks
Measure injector resistance with a multimeter and compare to manufacturer specs
Test injector power supply and pulse signal with a noid light
Use a scan tool to perform an injector balance test
Check fuel pressure and verify it holds within specification
Perform a fuel pressure drop test while each injector is activated
Use an oscilloscope to verify injector waveform and pulse width
Remove injectors and inspect spray pattern using an injector test bench
Clean or replace injectors if resistance, spray pattern, or flow is out of spec