Ford Mustang 1989-1993 Repair Guide

General Information


See Figure 1

The Thick Film Integrated (TFI-IV) ignition system is used for all EEC-IV electronic fuel-injected vehicles. The TFI-IV system module has six pins and uses an E-core ignition coil, named after the shape of the laminations making up the core.

There are two types of TFI-IV systems:

PUSH START- this first TFI-IV system featured a "push-start" mode which allowed manual transmission vehicles to be push started. Automatic transmission vehicles must not be push-started.
COMPUTER CONTROLLED DWELL- This second TFI-IV system features an EEC-IV controlled ignition coil charge time.

The TFI-IV ignition system with the Universal distributor has a distributor base mounted TFI ignition module and a Hall-effect stator assembly. The distributor also contains a provision to change the basic distributor calibration with the use of a replaceable retard (or octane) rod. The standard 0° calibration may be changed to either 3° or 6° retard rods. No other calibration changes are possible.

Initial timing adjustments are not required unless the distributor has been removed from the engine or moved from its initial factory setting.

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Fig. Fig. 1: TFI Module and pinouts

Both the PUSH START and COMPUTER CONTROLLED DWELL TFI-IV systems operate in the same manner. The TFI-IV module supplies voltage to the Profile Ignition Pickup (PIP) sensor, which sends 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. The EEC-IV module sends an electronic signal to the TFI-IV module to turn off the coil and produce a spark to fire the spark plug.


See Figures 2, 3 and 4

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 armature, made of ferrous metal, is used to trigger the Hall-effect switch. When the window of the armature is between the magnet and the Hall-effect device, a magnetic flux field is completed through the Hall-effect device and 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.

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Fig. Fig. 2: The rotary armature has open areas called windows and tabs called vanes

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Fig. Fig. 3: Magnetic flux through the Hall effect device when a window in the armature passes through the gap

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Fig. Fig. 4: The magnetic flux travels through the vane, not through the Hall effect device, when the vane passes through the gap