In 1986, Ford replaced the tried and true four-barrel carburetion setup with a sequential multiple-port fuel injection system. This new EFI-equipped 302 scared the heck out of many Mustang enthusiasts, but offered improved driveability, fuel mileage, and smooth performance. And while Ford hadn't quite worked the bugs out for hot rodders wanting to bolt on intake manifolds, heads, and some lumpy cams, the future would eventually be bright for EFI.
After some searching, I came...
After some searching, I came across Fiveology Racing (fiveologyracing.com). I spoke with Brian Bastob about the MAF conversion and ultimately my near future plans for the GT. Fiveology offers three conversion kits for varying performance needs, and Brian can put together a MAF conversion kit tailored specifically for the 5.0 Mustang. I also upgraded to a 70mm throttle body and EGR spacer, so Brian set me up accordingly. The kit is complete with everything you'll need minus the throttle body and EGR spacer. Brian is also knowledgeable about this conversion and was helpful with our tech questions.
Any radical modifications made to the speed density engine causes the said system to go "full tilt" (in pinball or poker terms) because the load/fuel mixture tables are inflexibly burned into the processor. If you exceed these parameters by installing a cam that's too big, or an induction that flows too much, then the system can no longer effectively compute injector pulse width (fuel/air ratio) and timing. The net result is a loss of driveability, an overly rich condition, or in extreme cases, engine failure due to detonation caused by lean mixtures and/or over-advanced timing.
Like most 5.0L fanatics, your author just can't leave it stock. I already have a pretty wicked '85 Mustang LX Coupe getting ready to be reassembled and I bought this particular '88 GT to be used as a daily driver. A promise to my wife to leave it stock turned into "it's just a couple of modifications, honey..." Married guys with Mustangs, you know the look that follows!
I knew that my '88 GT was a speed density car when I bought it, but now that I've started modifying it, I can't stop. I also know that before you can add any real performance modifications beyond cold-air intakes, gears, and exhaust on a '86-'88 speed-density-equipped 5.0L Mustang, you have to convert to mass airflow.
So here we are doing a mass air conversion on my Mustang. But first let's take a look at the difference between speed density and mass airflow.
Here is the engine in speed...
Here is the engine in speed density form.
Speed Density vs. Mass AirFlow
With a speed density system, actual intake manifold pressure is now measured using a manifold absolute pressure (MAP) sensor, as well as inlet air temperature (IAT), and in addition to the previously sensed TPS and engine rpm. Now the ECU fuel control programming includes a desired air/fuel ratio table, the injector flow rates, engine cubic inch displacement, a volumetric efficiency table, and the programs necessary to instantaneously calculate inlet airflow, required fuel flow (for the desired A/F ratio found in the A/F ratio table), and finally the correct injector pulse width.
Once the MAF is installed,...
Once the MAF is installed, you can see a clear difference in the inlet tract.
With mass airflow, the air entering the engine is actually measured using a mass airflow (MAF) sensor. Injector pulse width is still calculated in the same manner as shown previously, however, now the airflow is actually measured instead of calculated. In a sense, things happen before the fact, rather than after the fact. The big advantage of a MAF system is that you can change things on the engine that affect airflow and maintain driveability. In most cases, the MAF sensor will realize the change in airflow, and the fueling will still be correct. It makes the MAF system the most forgiving for engine modifications.
The first thing I did before buying any parts for my conversion was to do research. I decided I didn't want to waste time trying to scrounge parts from various salvage yards and hope I had everything I needed to complete my conversion.
'86-'88 Mass Air Conversion Installation
Once I had all my parts together, I drove the Mustang to Scatts Automotive, where John Scatterday performed most of the mass airflow conversion. We decided to disassemble the mechanical components before getting started on the wiring harness and EEC.
If you decide to use your stock throttle body, EGR spacer, and injectors, you can skip right over this section and move on to the mass airflow sensor wiring harness installation. Make certain to disconnect your battery first.
First we disconnected the...
First we disconnected the battery, then moved over to the other side of the engine compartment and removed the air box cover, clamps, and air intake hose.
Next we removed the breather...
Next we removed the breather hose from the throttle body and the two coolant hoses that are connected to the EGR spacer. We unplugged the wiring from the idle air control valve and removed the throttle position sensor from the throttle body. Once this was done, we removed the two bolts holding the throttle cable bracket in place and were able to pop the throttle cable off of the ball mount. Then we unplugged the wire harness from the EGR valve.
Four bolts hold down the throttle...
Four bolts hold down the throttle body and EGR spacer. Once we removed those, the throttle body and EGR spacer came right off. We turned the upper manifold's six bolts counterclockwise and removed it to access the fuel rails and injectors.
We unplugged the harness to...
We unplugged the harness to the injectors carefully and removed the two bolts holding the fuel rails. Once that was done, we carefully pulled out the stock 19-pound injectors. (Be sure the engine is cool because some fuel will leak/spray out.) Check for errant O-rings that may have come off the injectors and stayed in the fuel rail or injector ports in the intake manifold. Now the 24-lb/hr injectors can be installed, but before doing that, we applied a small amount of pre-assembly lube around the O-rings on both ends of the injectors. The injectors were then carefully pressed into the intake manifold ports.
The fuel rail is pressed down...
The fuel rail is pressed down on top of all four injectors simultaneously until you feel them all "pop" into place. Finally, we replaced the two bolts that secure the fuel rail to the intake manifold. We repeated these steps for the other side.
Working with the upper intake...
Working with the upper intake manifold, we removed the vacuum hose that is routed from the bottom of the upper intake manifold to the MAP sensor located on the firewall. Next, we capped off the vacuum port on the bottom of the upper intake manifold to prevent vacuum leaks. We left the MAP sensor port open to the atmosphere.
Now the upper intake manifold...
Now the upper intake manifold is ready to be mounted back onto the lower intake manifold. Make sure to reconnect all vacuum hoses before bolting the intake manifold down. A new upper intake manifold gasket is recommended when removing the upper intake manifold.
Mass AirFlow Wire Harness Wire Callouts
Red Wire-VPWR (Main Power) This wire must be spliced into pin 37 or 57 on the 60-pin main connector.
Black Wire-PWR GND (Main Ground) This wire must be spliced into pin 40 or 60 on the 60-pin main connector.
Green Wire-MAF RTN (Signal Ground)This wire/terminal must be inserted into location 9 on the 60-pin main connector.
White Wire-MAF RTN (Signal) This wire/terminal must be inserted into location 50 on the 60-pin main connector.
Time to fire it up!
Double check all wiring and everything in the engine compartment again before starting the vehicle. Before we buttoned everything up in the interior, we wanted to start the car to see how it runs, and if there were any issues that needed to be addressed.
Note the difference between...
Note the difference between the stock 60mm throttle body (left) and the new Accufab 70mm unit (right).
Please note that it is normal for the idle to be a little rough, and you may notice some slight surging while driving until the EEC relearns it's fuel curves. A couple hours will soon result in smooth driving.
We turned the key and the '88 GT fired right up! We were pleasantly surprised at how smooth the engine idled and we noticed a big difference in throttle response.
Once everything checked out OK, we slid the new EEC and wiring into place. Next, we installed the bolt for the EEC retaining bracket, and bolted down the ground wire and relay that were removed to get the old EEC out. After replacing both kick panels and scuff plates, we then replaced the driver's seat and any other trim pieces we had removed.
Wiring Note (see next eight photos): Some pre-'89 vehicles may require three black wires. If there are no terminals in the pin holes listed, you will need to add these wires. If your car doesn't have cruise control, you may have to add the speed sensor in the transmission. You'll need the speed sensor, an electrical connector, and a new speedometer cable. These should be available from your local Ford dealer. Some consider these three wires optional, but to avoid any issues with poor vehicle performance and/or EEC error codes, it is recommended that you install them.
Once the upper intake manifold...
Once the upper intake manifold was tightened up, we mounted the larger polished 70mm throttle body and billet machined EGR spacer from Accufab onto the upper intake manifold.
These shiny new parts offer...
These shiny new parts offer better throttle response, and deliver a lot more air to accompany the additional fuel being shot into the combustion chambers by larger 24-pound injectors.
For our conversion we are...
For our conversion we are installing a 73mm MAF meter, which will work well with our high-flowing Accufab 70mm throttle body, EGR spacer, and 24-lb/hr injectors. First, we needed to bolt the satin-black bracket with the three bolts to the MAF meter. Depending on whether you're using an aftermarket cold-air induction or even a supercharger, you may or may not need to use this bracket. Be sure to test-fit your MAF meter and bracket in place with your short-ram inlet before bolting everything together. That will help you to determine proper fitment and placement of your MAF meter assembly with your specific application. Also make sure your MAF meter is mounted in the correct direction according to the arrow molded into the top of the MAF connector.
Next we installed the aluminum...
Next we installed the aluminum short-ram tube that replaces the stock plastic air intake tube to the throttle body. We plan on installing the under hood kit to the ram-air hood, so we modified the short-ram tube to work with the stock air box. The short-ram tube was shortened by about 2 inches. Make sure to measure twice and cut once.
To connect the short-ram intake...
To connect the short-ram intake from the throttle body to the airbox, we chose to use high-quality silicone couplers and stainless steel T-bolt clamps from HoseTechniques. You will need two 3-inch inner diameter and one 3.5-inch inner diameter silicone coupler in 3-inch lengths. The HoseTechniques silicone couplers are manufactured to SAE J20 standards, -65 degrees F to 500 degrees F. The T-bolt clamps are also available in a polished finish. Slide the silicone hose couplers on and tighten them down with two clamps per coupler.
You can also purchase a high-flowing conical air filter and hose clamp that will mount onto your mass air meter housing if you do not want to use the stock airbox. Of course, most people bolt on an aftermarket cold-air intake kit.
It was necessary to remove...
It was necessary to remove the passenger-side lower kick panel. You may need to remove the door-sill scuff plate to remove the kick panel. Then pull out the insulation that is held in place by a plastic plug, and remove the white plastic retainer (and 8mm bolt) that holds the EEC in place. For easier access to the EEC, I also unbolted a ground wire and a green connector.
The four-wire harness from...
The four-wire harness from the mass air meter was routed through the firewall on the passenger side and down to the EEC main connector. An additional hole was made in the large oval-shaped grommet that the existing EEC harness is routed through, located in the upper corner on the passenger-side firewall. Be careful not to cut any existing wires while making a new hole in the grommet. Next, the end of the four-wire harness was taped to the end of a rigid piece of wire (protecting the EEC pins), and gently pushed through the grommet and down to the kick-panel area where we could pull it through. Make sure to leave a little slack in the four-wire harness and also use convoluted tubing to protect your wiring from chafing. To avoid possible leaks, we used some silicone to seal off the area where the new harness goes through the grommet.
Next We removed the black-plastic...
Next We removed the black-plastic wire retainer from the EEC main connector to access the wires. Then the H-shaped red-plastic pin lock on the other side of the EEC main connector was removed. We recommend using a hook-shaped awl (not a flat-head screwdriver) to gently pry out the pin lock. If the pin lock or connector is damaged, this could cause issues with the wires not remaining secure or connectivity problems in the main EEC connector.
We gently pulled the EEC down...
We gently pulled the EEC down as far as possible without pulling wires out of the main connector. Next we removed the main connector from the EEC by unbolting the 10mm bolt in the center of the connector, and we placed the EEC aside.
To ensure a trouble-free installation,...
To ensure a trouble-free installation, butt connectors are not suitable. We highly recommend soldering all wire connections. Do not cut or remove existing wires from your EEC main connector or wiring harness. Simply strip off about 0.75-inch of insulation, and solder the new wire to the existing wire.
Then tape the soldered joint...
Then tape the soldered joint securely. Now that you have located the four harness wires next to the EEC main connector, cut the wires to the correct length. Make sure that you leave enough length in the wire to account for placing the new computer up and inside the kick panel area.
Next John attached the two...
Next John attached the two supplied terminals to the green and white wires using a crimping tool, or you can carefully crimp them with pliers.
We needed to move the two...
We needed to move the two signals (wires with terminals) for the thermactor pump to different locations in the EEC connector. The wire/terminal currently in position 51 tan/red had to be relocated to position 38 of the EEC main connector. The wire/terminal currently in Position 11 green/black had to be relocated to Position 32 of the EEC main connector.
We unbolted the driver-side...
We unbolted the driver-side seat and removed it. Before you remove the seat, make sure to disconnect the connector. With access to the relay connector for the fuel pump monitor signal, the relay connector was unbolted from the floor to make it easier to splice in the wire.
Black Wire No. 1 (see wiring...
Black Wire No. 1 (see wiring note) was spliced into the pink/black wire going to the relay located under the driver's seat. The other end of the black wire/terminal was inserted into Position 19 of the EEC main connector. The relay was then bolted back down to the floor.
This signal, called FPM2,...
This signal, called FPM2, is used to monitor the voltage going to the fuel pump. It will generate an error code in the EEC if it's not connected. We routed the wiring up under the dashboard and over to the driver side. This helped us determine how much wire we were going to need and how much to cut off if necessary.
These signals are required...
These signals are required for cruise control and, as mentioned, there can be stalling on cars not equipped with cruise control. It will also generate an error code in the EEC if not installed. These signals come from a sensor that plugs into the transmission. There is an eight-pin connector behind the driver-side kick panel. Remove the driver-side kick panel and any insulation that may obstruct access to the connector. You may need to remove the door-sill scuff plate to remove the kick panel.
Black wire No. 2 (see wiring...
Black wire No. 2 (see wiring note) must be spliced into the orange/yellow wire. The other end of black wire No. 2, with the terminal on the end, was inserted into Position 6 of the EEC main connector. Black wire No. 3 was spliced into the dark green/white wire. The other end of black wire No. 3, with the terminal on the end, was inserted into Position 3 of the EEC main connector.
The red H-shaped pin lock...
The red H-shaped pin lock was replaced back into the EEC connector. We bolted the main connector to the new A9L MAF EEC; then snapped the black plastic wire retainer onto the EEC main connector. Make sure that your MAF four-pin connector is plugged into the MAF meter and the battery terminal is reconnected.
Before heading out to terrorize...
Before heading out to terrorize the neighborhood, there are a few more steps to perform. It is recommended to check the TPS calibration to eliminate any idle surge issues and for optimum driveability. We used the TPS calibration tool from Fiveology Racing, which allows us to clamp our voltage meter right up to the two metal terminals without having to stab into the TPS wiring. Everything checked out great on our '88 GT; our TPS voltage was dialed in at 0.967 volts.