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.
SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSMERCURY1991TRACER BASE, 4D SEDAN, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 57 (ENGINE CONTROLS - SYSTEM/COMPONENT TESTS - EEC (1.8L))ENGINE SENSORS & SWITCHESOXYGEN SENSOR (O2S)
1991 Mercury Tracer Base, 4D Sedan, Automatic
Oxygen Sensor (O2S)
1991 Mercury Tracer Base, 4D Sedan, AutomaticSECTION Oxygen Sensor (O2S)
WARNING: This page is about a different car, the 1994 Mercury Tracer and 1994 Ford Escort. However, it is still accessible from the selected car via links, so may be relevant.
Continuously rich or lean operation may be caused by malfunction other than O2S. Faults in O2S should set fault code in PCM memory. See CIRCUIT TEST O2S in TESTS W/CODES - EEC 1.8L article in the ENGINE PERFORMANCE section.
RENDER: 1.0x
NO RELATED
Recommended Tools & Savings
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.