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 3 (ENGINE CONTROLS - TESTS W/CODES - EEC)SELF-DIAGNOSTIC SYSTEMRETRIEVING CODESVISUAL CHECK & VEHICLE PREPARATION
1991 Mercury Tracer Base, 4D Sedan, Automatic
Visual Check & Vehicle Preparation
1991 Mercury Tracer Base, 4D Sedan, AutomaticSECTION Visual Check & Vehicle Preparation
WARNING: This page is about a different car, the 1992 Mercury Tracer, 1992 Ford Probe, and 1992 Ford Escort. However, it is still accessible from the selected car via links, so may be relevant.
Before hooking up any equipment to diagnose EEC system, visually check the following, and perform preparation procedures:
- Check condition of air cleaner and air ducting.
- Perform all necessary safety precautions to prevent personal injury or vehicle damage.
- Block drive wheels. Set parking brake. Place shift lever in Park A/T) or Neutral (M/T). DO NOT move shift lever during test unless specifically directed to do so.
- Check all vacuum hoses for leaks, restrictions and proper routing.
- Check EEC system wiring harness connections for corrosion, damaged pins, loose wires and proper routing.
- Check ECA, sensors and actuators for physical damage.
- Check engine coolant and oil level.
- Turn off all lights and accessories. Ensure vehicle doors are closed when measuring voltage or resistance.
- Start engine and allow it to idle until upper radiator hose is hot and pressurized. Check for leaks around exhaust manifold and exhaust gas oxygen sensor.
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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.