Tfi Manual Or Auto?

That is an error in the parts listing. There is only 1 correct TFI or the 86-93 5.0 Mustangs. It is gray.

TFI module description courtesy of Tmoss

Well, if you include the SN95 style TFI, there are four TFI modules. Two for the distributor mounted style are black and gray and have the pins comming out of the top to plug into the distributor. The SN95 style also has black and gray modules without the pins because they are remotely mounted. The gray modules are "push start" modules.

Ignition dwell with the Push Start (gray module) system is controlled by the TFI module alone, and increases with engine rpm. The Ignition Diagnostic Monitor (IDM) signal on a Push Start TFI system comes from the coil negative circuit and is filtered through a 22k ohm resistor to pin #4 on the EEC-IV computer. The computer monitors this circuit to verify a coil firing for each PIP signal, and sets codes if it sees missing or erratic signals. Another feature that is unique to the Push Start TFI system is the start input on pin #4 of the module connector. This is wired into the starter relay trigger circuit, and signals the TFI module that the engine is cranking. When the module sees battery voltage on this circuit, the SPOUT signal is ignored.

In the early '90s, Ford began using a different TFI system on certain vehicles -- the Computer Controlled Dwell (CCD) TFI system. The TFI module on CCD TFI is always black in color. There are a few major differences between the two systems. As the name implies, with the CCD system, the computer controls primary dwell. The CCD TFI module still ungrounds (fires) the coil at the rising edge of the SPOUT signal, but now the falling edge of the SPOUT signal (which had no meaning to the Push Start TFI module) is used by the CCD TFI module to ground the coil. The PIP signal remains the same 50% duty cycle square wave, but SPOUT signal duty cycle varies according to how much dwell is desired by the computer.

Another major difference between the two systems is the IDM circuit. Pin #4 on the CCD TFI module, which was the start circuit input on the Push Start TFI module, is now the IDM signal, sent directly from the TFI module to pin #4 on the EEC-IV computer. This signal is still a filtered (low voltage) version of the ignition primary waveform, but is filtered internally in the TFI module rather than through an external resistor. There isn't any start circuit input to the CCD TFI module; the module infers engine cranking from a low rpm input from the PIP signal.
Since these two TFI systems are so significantly different, yet so similar in appearance, parts application problems will inevitably occur. A gray Push Start TFI module will plug right into a CCD system, and vice versa. To make matters worse, parts books are often incorrect on TFI module applications! With the incorrect TFI module installed, the vehicle will run, but drivability and MIL (malfunction indicator lamp) problems will result. For instance, if a gray Push Start TFI module is installed in a CCD system, the computer will not be able to control ignition dwell, and the MIL will illuminate with memory codes for the IDM circuit set, as the gray TFI module is incapable of generating an IDM signal to the computer. If a black CCD TFI module is installed in a Push Start system, dwell will remain fixed, since the SPOUT signal duty cycle never changes. If in doubt about which TFI module belongs on a particular vehicle, consult the ignition system-wiring diagram for the vehicle. If the wire going to pin #4 on the EEC-IV computer comes directly from pin #4 of the TFI module, it is a CCD system. If not, it is a Push Start system.

TFI module differences & pinout



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Tom (Torque) Moss
88GT Vert 5spd 3:08, ported lower, flowmaster 2.5"catbacks, K&N, 13° timing, 219RWHP 290RWTQ SAE Corrected, 261RWTQ Average 2,000-5,200 rpm

As of 4/25/04, stock cam advanced 4°, NMRA prepped F/S GT40P heads with 1.6 Scorpion rockers, MAC P headers Jet-Hot coated, 97 Exlporer intake, TB and injectors with lower ported by me. 1st untuned dyno - 257RWHP 309RWTQ (SAE), 284RWTQ average 2,000-5,600 rpm.