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Fuel Injector Check

WARNING: This page does not describe the selected car, but rather 11 other vehicles, including the 1991 Ford Ranger, 1991 Ford RV Cutaway, 1991 Ford Pickup, 1991 Ford F-Super Duty, and 1991 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.
  1. Connect tachometer to engine. Run engine at idle. Disconnect and reconnect injectors individually. If each injector causes a momentary drop in engine speed of at least 100 RPM, injectors are providing proper fuel delivery. RPM drop should only be momentary, as ISC will attempt to re-establish correct idle RPM.
  2. Replace any injectors not causing sufficient drop in engine speed. When test is complete, turn engine off. To check curb idle, refer to emission control specifications on decal in engine compartment or IDLE SPEED & MIXTURE in ADJUSTMENTS article in the ENGINE PERFORMANCE Section.
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