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 64 (ENGINE CONTROLS - BASIC TESTING - V8)IGNITION CHECKSELECTRONIC IGNITION (EI) (HIGH DATA RATE) SYSTEMSPARK CHECK
1991 Mercury Tracer Base, 4D Sedan, Automatic
Spark Check
1991 Mercury Tracer Base, 4D Sedan, AutomaticSECTION Spark Check
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 1994 Mercury Grand Marquis, 1994 Mercury Cougar, 1994 Lincoln Town Car, 1994 Lincoln Mark VIII, and 1994 Ford Thunderbird. However, it is still accessible from the selected car via links, so may be relevant.
- Check the EI (high data rate) system (formerly Electronic Distributorless Ignition System - EDIS) for fault codes and repair if necessary. See QUICK TEST in appropriate TESTS W/CODES
article listed below. If no fault codes are present, check ignition system wiring harness connectors for corrosion and tight fit. See Fig 1
, or 3. Clean or repair connectors as necessary.
- TESTS W/CODES - EEC-IV (5.0L) (for Mustang)
- TESTS W/CODES - EEC-V (4.6L) (for Cougar & Thunderbird 4.6L)
- TESTS W/CODES - EEC-IV (4.6L) (all other 4.6L)
- If wiring and connectors are okay, use Neon Bulb Spark Tester (D89P-6666-A) to check for spark at each spark plug wire while cranking engine. If spark is strong and consistent at each spark plug (one spark per crankshaft revolution), ignition system is okay. If spark is not present, proceed to IGNITION SYSTEMS in appropriate I - SYS/COMP TESTS article. Refer to the following menu:
- SYSTEM/COMPONENT TESTS - EEC-IV (5.0L) (for Mustang)
- SYSTEM/COMPONENT TESTS - EEC-V (for Cougar & Thunderbird 4.6L)
- SYSTEM/COMPONENT TESTS - EEC-IV (4.6L) (all other 4.6L)
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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.