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.
1991 Ford Taurus L4-153 2.5L HSCFACTORY OEM SERVICE PROCEDURE
Testing Notes
Diagnostic Reference Value Notes
1. Diagnostic reference values are based on engine warmed to normal operating temperature.
2. Key On Engine Off (KOEO) and hot idle values are recorded with the vehicle in NEUTRAL.
3. Before proceeding with timing checks, the monitor must be calibrated to base timing. Base timing equals 10 degrees.
4. Use THIRD GEAR for 30 mph values and FOURTH GEAR for 55 mph values.
5. Reference values shown in the charts may differ between vehicles due to component tolerances, driving conditions, weather, etc. These values were recorded at approximately 600 feet above sea level and ambient temperatures ranging from 50 to 70 degrees Fahrenheit. Some EEC-IV devices are temperature dependent and their values may vary greatly. Other values are calibration dependent and may also vary.
1. Diagnostic reference values are based on engine warmed to normal operating temperature.
2. Key On Engine Off (KOEO) and hot idle values are recorded with the vehicle in NEUTRAL.
3. Before proceeding with timing checks, the monitor must be calibrated to base timing. Base timing equals 10 degrees.
4. Use THIRD GEAR for 30 mph values and FOURTH GEAR for 55 mph values.
5. Reference values shown in the charts may differ between vehicles due to component tolerances, driving conditions, weather, etc. These values were recorded at approximately 600 feet above sea level and ambient temperatures ranging from 50 to 70 degrees Fahrenheit. Some EEC-IV devices are temperature dependent and their values may vary greatly. Other values are calibration dependent and may also vary.
Factory Service Tools
Use the Manual With the Right Hardware
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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.
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