Eight from Four: Fox Mustang 2.3L to 5.0L Swap Guide

One of the lines from the vacuum canister goes to the EGR valve, shownhere. The EGR is a diaphragm that opens and closes to recirculate thegases it picks up from the exhaust crossover in the lower tank.

The four-cylinder throttle cable is too short for a V-8. You must usethe V-8 throttle cable and bracket.

One of the most difficult parts to find is an EFI wiring harness, whichis composed of three separate segments. The underdash portion of theharness is common to the four-cylinder and the V-8. This top portioncomes out of the dash on the passenger side and is routed to thecomputer, the mass air meter, the coil, and the starter solenoid.

Coils are the same on four-cylinders and V-8s for all model years. So,all you have to do here is unplug the four-cylinder harness and plug inthe V-8 harness.

The MAP (manifold air pressure) sensor, mounted on the top and center ofthe firewall, is different from a four to a V-8 and must be changed.There are also two different V-8 MAP sensors, one for speed density fuelinjection ('86-'88, which uses a vacuum line) and one for mass-air fuelinjection ('89-'93). The two V-8 MAP sensors look almost identical.Using the incorrect MAP sensor will cause a bad surge and idle problems.

The V-8 also requires a unique vacuum distributor. It distributes vacuumfor various functions, such as the brakes, air conditioning, and cruisecontrol.

Placed side by side, the vacuum distributor for the four-cylinder (left)is much smaller and of a different configuration than the one for theV-8.

The front segment of the wiring harness ties into the headlights,parking lights, turn signals, the horn, and the alternator. On afour-cylinder, the alternator is on the driver side. On the V-8, thealternator is on the passenger side. Therefore, the four-cylinder frontharness is shorter and must be changed.

There are two different types of V-8 wiring harnesses for thefuel-injected engine. The V-8 harness for '86-'89 EFI motors has a blackplug to the alternator (left). The V-8 harness for '90-'93 EFI motorshas a blue plug (right). Notice the terminals are also different inside.

The blue plug mates with a blue alternator connection. Black goes withblack. If you plug black and blue together, the alternator won't chargethe battery.

A four-cylinder computer will not run a V-8. The V-8 computer has moreterminals than the four-cylinder computer.

The V-8 computer and the four-cylinder computer plug into the wiringharness in the same location under the dash. The '86-'88 computersoperate speed density, fuel-injected motors. The '89-'93 computersoperate mass-air, fuel-injected motors. The '89 computer stands alonebecause in 1990, Ford went to an airbag.