Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSMERCURY1991TRACER BASE, 4D SEDAN, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 110 (ENGINE CONTROLS - BASIC TESTING - 4.6L)FUEL SYSTEMFUEL INJECTORSFUEL INJECTOR CHECK
1991 Mercury Tracer Base, 4D Sedan, Automatic
Fuel Injector Check
1991 Mercury Tracer Base, 4D Sedan, AutomaticSECTION Fuel Injector Check
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 1995 Mercury Grand Marquis, 1995 Mercury Cougar, 1995 Lincoln Town Car, 1995 Lincoln Continental, and 1995 Ford Thunderbird. However, it is still accessible from the selected car via links, so may be relevant.
- Connect tachometer to engine. Run engine at idle. Disconnect and reconnect injectors individually. When disconnected, each injector should cause a momentary drop in engine speed of at least 100 RPM. Engine RPM drop should only be momentary as Powertrain Control Unit (PCM) will attempt to re-establish correct idle RPM.
- Replace any injectors that do not cause sufficient drop in engine speed. When test is complete, check idle speed. Refer to emission control specifications on decal in engine compartment. See IDLE SPEED & IGNITION TIMING.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.