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 Explorer 4D Utility, RWD, StandardFACTORY OEM SERVICE PROCEDURE
Ignition System Identification
NOTE:
For additional information and descriptions see IGNITION SYSTEMS in THEORY/OPERATION
article in the ENGINE PERFORMANCE Section. Perform spark output check in BASIC TESTING
article before entering these tests. Some ignition systems require that Quick Test procedure be performed prior to testing. This will retrieve trouble codes from the EEC-IV system. See TESTS W/CODES
EEC-IV article.
IGNITION SYSTEM ACRONYMS (1)
| Acronym | Definition | ||
|---|---|---|---|
| BAT+ or BAT(+) | Battery Positive | ||
| BAT or BAT(-) | Battery Negative | ||
| BOB | Breakout Box | ||
| CBD | Closed Bowl Distributor (TFI-IV) | ||
| CCD | Computer Controlled Dwell (TFI-IV) | ||
| CID | Cylinder Identification | ||
| C1, C2, C3 | Coil Drive (Coils 1, 2 & 3) | ||
| DIS | Distributorless Ignition System | ||
| ECA | Electronic Control Assembly (EEC-Processor, Computer, Processor) | ||
| EDIS | Electronic Distributorless Ignition System | ||
| DPI | Dual Plug Inhibit (High Signal - Rt Plugs Fire, Low Signal -Both Sides Fire) | ||
| IDM | Ignition Diagnostic Monitor (Diagnostic Signal to ECA) | ||
| IGGND | Ignition Ground (Low Current Ground Reference) | ||
| KOEC | Key On Engine Cranking (Testing Condition | ||
| KOEO | Key On Engine Off (Testing Condition) | ||
| KOER | Key On Engine Running (Testing Condition) | ||
| PIP | Profile Ignition Pickup (Crankshaft Sensor Signal) | ||
| PWRGND | Power Ground Circuit to DIS Module | ||
| SAW | Spark Angle Word | ||
| SPOUT | Spark Output (ECA Spark Control Signal) | ||
| TFI or TFI-IV | Thick Film Ignition (IV is 4th Generation) | ||
| VPWR or VBAT | Battery Power or Battery Voltage | ||
| VRS or VR Sensor | Variable Reluctance Sensor (Crankshaft) | ||
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IGNITION SYSTEM IDENTIFICATION
| Application | System | ||
|---|---|---|---|
| 2.3L Ranger | DIS | ||
| 2.9L Ranger | TFI-IV | ||
| 3.0L Aerostar & Ranger | TFI-IV | ||
| 4.0L Aerostar, Explorer, Navajo & Ranger | EDIS | ||
| 4.9L Bronco, "E" & "F" Series | TFI-IV | ||
| 5.0L Bronco, "E" & "F" Series | TFI-IV | ||
| 5.8L Bronco, "E" & "F" Series | TFI-IV | ||
| 7.5L "E" & "F" Series | (1) TFI-IV | ||
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Factory Service Tools
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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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