Test H: Step 8

8) Injector Balance Test  Connect tachometer to engine. Start and run engine at idle. Disconnect and reconnect injectors one at a time. Note RPM drop for each injector. Each injector should produce a momentary RPM drop of about 100 RPM. Note that ISC will attempt to re-establish correct RPM. If each injector does not produce at least 100 RPM drop when disconnected, service or replace faulty injector(s) and repeat QUICK TEST. If RPM drop is correct for all injectors, fuel delivery is okay. Problem is in area common to all cylinders such as a vacuum leak, fuel contamination, EGR, or HEGO ground. Check MAP frequency, etc.