Ford Pick-ups and Broncos 1987-1996 Repair Guide

TFI-IV System



See Figures 1 and 2

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Fig. Fig. 1: TFI schematic

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Fig. Fig. 2: Exploded view of the TFI components

The Thick Film Integrated (TFI-IV) ignition system uses a camshaft driven distributor with no centrifugal or vacuum advance. The distributor has a diecast base, incorporating a Hall effect stator assembly. The TFI-IV system module is mounted on the distributor base, it has 6 pins and uses an E-Core ignition coil, named after the shape of the laminations making up the core.

The TFI-IV module supplies voltage to the Profile Ignition Pick-up (PIP) sensor, which sends the crankshaft position information to the TFI-IV module. The TFI-IV module then sends this information to the EEC-IV module, which determines the spark timing and sends an electronic signal to the TFI-IV ignition module to turn off the coil and produce a spark to fire the spark plug.

The operation of the universal distributor is accomplished through the Hall effect stator assembly, causing the ignition coil to be switched off and on by the EEC-IV computer and TFI-IV modules. The vane switch is an encapsulated package consisting of a Hall sensor on one side and a permanent magnet on the other side.

A rotary vane cup, made of ferrous metal, is used to trigger the Hall effect switch. When the window of the vane cup is between the magnet and the Hall effect device, a magnetic flux field is completed from the magnet through the Hall effect device back to the magnet. As the vane passes through the opening, the flux lines are shunted through the vane and back to the magnet. A voltage is produced while the vane passes through the opening. When the vane clears the opening, the window causes the signal to go to 0 volts. The signal is then used by the EEC-IV system for crankshaft position sensing and the computation of the desired spark advance based on the engine demand and calibration. The voltage distribution is accomplished through a conventional rotor, cap and ignition wires.


Spark Plug Wire Resistance

Whenever the high tension wires are removed from the plugs, coil, or distributor, silicone grease must be applied to the boot before reconnection. Use a clean small screwdriver blade to coat the entire interior surface with Ford silicone grease D7AZ-19A331-A, Dow Corning #111, or General Electric G-627.

  1. Use spark plug wire removal pliers, or grasp firmly at the boot (not the wire itself) and remove the wires from the plugs, then remove the distributor cap.
  3. Measure the resistance through the distributor cap at that end. Resistance on these wires must not exceed 5,000 ohms per foot. Do not pierce any ignition wire for any reason. Measure only from the two ends.


The air gap between the armature and magnetic pick-up coil in the distributor is not adjustable, nor are there any adjustment for the amplifier module. Inoperative components are simply replaced. Any attempt to connect component