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 116 (ENGINE CONTROLS - THEORY & OPERATION - EEC-IV 4.6L)
1991 Mercury Tracer Base, 4D Sedan, Automatic
Section 116 (Engine Controls - Theory & Operation - EEC-IV 4.6L)
1991 Mercury Tracer Base, 4D Sedan, AutomaticSECTION Section 116 (Engine Controls - Theory & Operation - EEC-IV 4.6L)
WARNING: This page is about a different car, the 1994 Mercury Grand Marquis, 1994 Lincoln Town Car, 1994 Lincoln Mark VIII, and 1994 Ford Crown Victoria. 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.