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 120 (ENGINE CONTROLS - THEORY & OPERATION - EEC-IV 2.3L)
1991 Mercury Tracer Base, 4D Sedan, Automatic
Section 120 (Engine Controls - Theory & Operation - EEC-IV 2.3L)
1991 Mercury Tracer Base, 4D Sedan, AutomaticSECTION Section 120 (Engine Controls - Theory & Operation - EEC-IV 2.3L)
WARNING: This page is about a different car, the 1994 Mercury Topaz and 1994 Ford Tempo. However, it is still accessible from the selected car via links, so may be relevant.
- Introduction
- Air Induction System
- Computerized Engine Controls
- Control Unit
- Input Devices
- Notes
- Barometric Pressure (BARO) Sensor
- Brake On/Off (BOO) Switch
- Camshaft Position (CMP) Sensor
- Clutch Pedal Position (CPP) Switch
- Coolant Temperature Sensor
- Crankshaft Position (CKP) Sensor
- Data Link Connector (DLC) & Self-Test Input (STI) Connector
- Differential Pressure Feedback EGR (DPFE) Sensor
- Exhaust Gas Recirculation Temperature (EGRT) Sensor
- EGR Valve Position (EVP) Sensor
- Engine Coolant Temperature (ECT) Sensor
- Flexible Fuel (FF) Sensor
- Heated Oxygen Sensor (HO2S)
- Intake Air Temperature (IAT) Sensor
- Knock Sensor (KS)
- Manifold Absolute Pressure (MAP) Sensor
- Manual Lever Position (MLP) Sensor
- Mass Airflow (MAF) Sensor
- Park/Neutral Position (PNP) Switch
- Power Steering Pressure (PSP) Switch
- Pressure Feedback EGR (PFE) Sensor
- Programmable Speedometer/Odometer Module (PSOM)
- Throttle Position (TP) Sensor
- Transmission Fluid Temperature (TFT) Sensor
- Transmission Speed Sensor (TSS)
- Vehicle Speed Sensor (VSS)
- Output Signals
- Fuel System
- Ignition System
- Emission Systems
- Notes
- Air Cleaner Temperature Sensor
- Temperature Vacuum Switch (TVS)
- Vacuum Control Switches
- Vacuum Delay Valves
- Vacuum Reservoir
- Vacuum RESTRICTOR
- Vacuum Vent Valves
- Air Injection Systems
- Notes
- Pulsed Secondary Air Injection (PAIR) System
- Secondary Air Injection (AIR) System
- Air By-Pass (AIRB) Valve
- Pulsed Secondary Air Injection (PAIR) Valve
- Air Injection Diverter (AIRD) Valve
- Air Injection (AIR) Solenoid
- Air Pump
- Air Silencer/Filter
- Check Valve
- Combination Air Injection By-Pass (AIRB) & Air Injection Diverter (AIRD) Valve
- Dual Air Control Solenoids
- EGR System
- Evaporative Emission System
- Positive Crankcase Ventilation (PCV)
- Self-Diagnostic System
- Miscellaneous Controls
- Wiring Diagrams
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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.