Air and Fuel Control
The throttle body assembly is comprised of six individual components which perform the job of mixing the air and fuel to the ideal ratio for controlling exhaust emissions and providing performance and economy. The six components are: air control, fuel injector nozzles, fuel pressure regulator, fuel pressure diagnostic valve, cold engine speed control, and throttle position sensor.Air Control
Air flow to the engine is controlled by two butterfly valves mounted in a two piece, die-cast aluminum housing called the throttle body. The butterfly valves, or throttle valves, are identical in design to the throttle plates of a conventional carburetor and are actuated by a similar linkage and pedal cable arrangement.Fuel Injector Nozzles
The fuel injector nozzles are mounted in the throttle body and are electromechanical devices which meter and atomize the fuel delivered to the engine. The injector valve bodies consist of a solenoid actuated pintle and needle valve assembly. An electrical control signal from the EED electronic processor activates the solenoid causing the pintle to move inward off its seat and allowing fuel to flow. the fuel flow through the injector is controlled by the amount of time the injector solenoid holds the pintle off its seat.Fuel Pressure Regulator
The fuel pressure regulator is mounted on the throttle body. The regulator smooths out fuel pressure drops from the fuel pump. It is not sensitive to back pressure in the return line to the tank.
A second function of the pressure regulator is to maintain fuel supply pressure upon engine and fuel pump shut down. The regulator acts as a check valve and traps fuel between itself and the fuel pump. This promotes rapid start ups and helps prevent fuel vapor formation in the lines, or vapor lock. The regulator makes sure that the pressure of the fuel at the injector nozzles stays at a constant 39 psi.Fuel Pressure Diagnostic Valve
A Schrader-type diagnostic pressure valve is located at the top of the throttle body. This valve can be used by service personnel to monitor fuel pressure, bleed down the system pressure prior to maintenance and to bleed out air which may have been introduced during assembly or filter servicing. A special Ford Tool (T80L-9974-A) is used to accomplish these procedures.
Cold Engine Speed Control
The cold engine speed control serves the same purpose as the fast idle speed device on a carbureted engine, which is to raise engine speed during cold engine idle. A throttle stop cam positioner is used. the cam is positioned by a bimetal spring and an electric heating element. The cold engine speed control is attached to the throttle body. As the engine heats up, the fast idle cam on the cold engine speed control is gradually repositioned by the bimetal spring, heating element and EEC computer until normal idle speed is reached. The EEC computer automatically kicks down the fast idle cam to a lower step (lower engine speed) by supplying vacuum to the automatic kickdown motor which physically moves the high speed cam a predetermined time after the engine starts.Throttle Position Sensor
This sensor is attached to the throttle body and is used to monitor changes in throttle plate position. the throttle position sensor sends this information to the computer, which uses it to select proper air/fuel mixture, spark timing and EGR control under different engine operating conditions.Fuel System Inertia Switch
In the event of a collision, the electrical contacts in the inertia switch open and the fuel pump automatically shuts off. The fuel pump will shut off even if the engine does not stop running. The engine, however, will stop a few seconds after the fuel pump stops. It is not possible to restart the engine until the inertia switch is manually reset. The switch is located in the luggage compartment on the left hinge support on all models to 1988. 1989-91 models, LH lower back panel in luggage compartment. To reset, depress both buttons on the switch at the same time (Some models use only one button).
Diagnostic and test procedures on the EEC-III and EEC-IV electronic control system require special test equipment. Have the testing done by a professional.Fuel Pressure Tests
The diagnostic pressure valve (Schrader type) is located at the top of the Fuel charging main body. This valve provides a convenient point for service personnel to monitor fuel pressure, bleed down the system pressure prior to maintenance, and to bleed out air which may become trapped in the system during filter replacement. A pressure gauge with a adapter is required to perform pressure tests.
System Pressure Test
Testing fuel pressure requires the use of a special pressure gauge (T80L-9974-A or equivalent) that attaches to the diagnostic pressure tap on the fuel charging assembly. Depressurize the fuel system before disconnecting any lines.
- Disconnect the fuel return line at the throttle body (in-tank high pressure pump) and connect the hose to a 1 quart calibrated container. Connect a pressure gauge.
- Disconnect the electrical connector at the fuel pump. The connector is located ahead of fuel tank (in-tank high pressure pump) or just forward of pump outlet (in-line high pressure pump). Connect an auxiliary wiring harness to the connector of the fuel pump. Energize the pump for 10 seconds by applying 12 volts to the auxiliary harness connector, allowing the fuel to drain into the calibrated container. Note the fuel volume and pressure gauge reading.
- Correct fuel pressure should be 35-45 psi (241-310 kPa). Fuel volume should be 10 oz. in 10 seconds (minimum) and fuel pressure should maintain a minimum of 30 psi (206 kPa) immediately after pump cut-off.
If the pressure condition is met, but the fuel flow is not, check for blocked filter(s) and fuel supply lines. After correcting the problem, repeat the test procedure. If the fuel flow is still inadequate, replace the high pressure pump. If the flow specification is met but the pressure is not, check for a worn or damaged pressure regulator valve on the throttle body. If both the pressure and fuel flow specifications are met, but the pressure drops excessively after de-energizing, check for a leaking injector valve(s) and/or pressure regulator valve. If the injector valves and pressure regulator valve are okay, replace the high pressure pump. If no pressure or flow is seen in the fuel system, check for blocked filters and fuel lines. If no trouble is found, replace the in-line fuel pump, in-tank fuel pump and the fuel filter inside the tank.Fuel Injector Pressure Test
- Connect pressure gauge T80L-9974-A, or equivalent, to the fuel pressure test fitting. Disconnect the coil connector from the coil. Disconnect the electrical lead from one injector and pressurize the fuel system. Disable the fuel pump by disconnecting the inertia switch or the fuel pump relay and observe the pressure gauge reading.
- Crank the engine for 2 seconds. Turn the ignition OFF and wait 5 seconds, then observe the pressure drop. If the pressure drop is 2-16 psi (14-110 kPa), the injector is operating properly. Reconnect the injector, activate the fuel pump, then repeat the procedure for other injector.
- If the pressure drop is less than 2 psi (14 kPa) or more than 16 psi (110 kPa), switch the electrical connectors on injectors and repeat the test. If the pressure drop is still incorrect, replace the disconnected injector with one of the same color code, then reconnect both injectors properly and repeat the test.
- Disconnect and plug the vacuum hose at EGR valve. It may be necessary to disconnect the idle speed control (3.8L) or the throttle kicker solenoid (5.0L) and use the throttle body stop screw to set the engine speed. Start and run the engine at 1,800 rpm (2,000 rpm on 1984 and later models). Disconnect the left injector electrical connector. Note the rpm after the engine stabilizes (around 1,200 rpm). Reconnect the injector and allow the engine to return to high idle.
- Perform the same procedure for the right injector. Note the difference between the rpm readings of the left and right injectors. If the difference is 100 rpm or less, check the oxygen sensor. If the difference is more than 100 rpm, replace both injectors.
REMOVAL & INSTALLATION
- Remove the air cleaner assembly.
- Release the pressure from the fuel system at the diagnostic valve on the throttle body using SST T80L-9974-A or equivalent.
- Disconnect the throttle cable and transmission valve lever.
- Disconnect the fuel, vacuum and electrical connections.
Either the multi or single ten pin connections may be encountered. To disconnect the electrical ten pin connectors, push in or squeeze on the right side lower locking tab while pulling up on the connection. Multi connectors disconnect by pulling apart. The ISC connector tab must be moved out while pulling them apart.
- Remove the throttle body assembly retaining nuts, then remove the unit.
- Remove the mounting gasket from the intake manifold.
- Clean the gasket mounting surfaces and place a spacer and gaskets on the intake manifold. Position the throttle body assembly on the spacer and gasket.
- Secure the throttle body assembly with the retaining nut, tighten to 10 ft. lbs. (14 Nm). To prevent any leakage, distortion or damage to the throttle body flange, snug the nuts, then in an alternately fashion; tighten each nut in a criss-cross pattern.
- Connect the fuel line, electrical connections, throttle cable and all emission lines.
- Start the engine, check for leaks. Adjust the engine idle if necessary.
DISASSEMBLY AND ASSEMBLY
See Figures 1 through 12
- Remove the air cleaner mounting stud in order to separate the upper body from the throttle body.
- Turn the fuel charging assembly (throttle body) over and remove the four screws from the bottom of the throttle body.
- Separate the throttle body (lower half) from the main body (upper half).
- Remove the old gasket. If it is stuck and scraping is necessary, use only a plastic or wood scraper. Take care not to damage the gasket surfaces.
- Remove the three pressure regulator mounting screws. Remove the pressure regulator.
- Disconnect the electrical connectors at each injector by pulling outward on the connector and not on the wire. Loosen, but do not remove the wiring harness retaining screw. Push in on the harness tab's to remove it from the upper body.
- Remove the fuel injector retaining screw. Remove the injection retainer.
- Pull the injectors, one at a time, from the upper body. Mark the injectors for identification. They must be reinstalled in the same position (choke or throttle side). Each injector is equipped with a small O-ring. If the O-ring does not come out with the injector, carefully pick out of body.
- Remove the fuel diagnostic valve assembly.
- Remove the choke cover by drilling the retaining rivets. A 1 / 8 in. (3mm) or No. 30 drill is required. A choke mounting kit for installation is available from Ford.
- Remove the choke cap retaining ring, choke cap and gasket. Remove the thermostat lever screw and lever. Remove the fast idle cam assembly and control rod positioner.
- Hold the control diaphragm cover in position and remove the two mounting screws. Carefully remove the cover, spring and pull down diaphragm.
- Remove the fast idle retaining nut, fast idle cam adjuster lever, fast idle lever and E-clip.
- Remove the potentiometer (sensor) connector bracket retaining screw. Mark the throttle body and throttle position sensor for correct installation position. Remove the throttle sensor retaining screws and slide the sensor off of the throttle shaft. Remove the throttle positioner retaining screw and remove the throttle positioner.
- Perform any necessary cleaning or repair.
- Assemble the upper body by first installing the fuel diagnostic fuel pressure valve assembly.
- Lubricate the new injector O-rings with a light grade oil. Install the O-rings on each injector. Install the injectors in their appropriate choke or throttle side position. Use a light, twisting, pushing motion to install the injectors.
- Install the injector retainer and tighten the retaining screw to 30-60 inch lbs. (3-7 Nm).
- Install the injector wiring harness and snap into position. Tighten the harness retaining screw to 8-10 inch lbs. (0.8-1.1 Nm).
- Snap the electrical connectors into position on the injectors. Lubricate the fuel pressure regulator O-ring with light oil. Install the O-ring and new gasket on the regulator. Install the regulator and tighten retaining screws to 27-40 inch lbs. (2-4 Nm).
- Install the throttle positioner onto the throttle body. Tighten the retaining screw to 32-44 inch lbs. (3-5 Nm).
- Hold the throttle sensor (potentiometer) with the location identification mark (see the last removal step) in the 12 o'clock position. The two rotary tangs should be at 3 o'clock and 9 o'clock positions.
- Slide the sensor onto the throttle shaft with the identification mark still in the 12 o'clock position. Hold the sensor firmly against the throttle body.
- Rotate the sensor until the identification marks on the sensor and body are aligned. Install the retaining screws and tighten to 13-18 inch lbs. (1-2 Nm).
- Install the sensor wiring harness bracket retaining screw. Tighten to 18-22 inch lbs. (2.0-2.4 Nm). Install the E-clip, fast idle lever, fast idle adjustment lever and fast idle retaining nut. Tighten the retaining nut to 16-20 inch lbs. (1-2 Nm)
- Install the pull down diaphragm, spring and cover. Hold the cover in position and tighten the retaining screws to 13-19 inch lbs. (1-2 Nm).
- Install the fast idle control rod positioner, fast idle cam and the thermostat lever. Tighten the retaining screw to 13-19 inch lbs. (1-2 Nm).
- Install the choke cap gasket, bimetal spring, cap and retaining ring. Install new rivets and snug them with the rivet gun. Do not break rivets. Loosely install so choke cover can rotate. Index choke and break rivets to tighten.
- Install the gasket between the main body and the throttle body. Place the throttle body in position. Install the four retaining screws loosely. Install the air cleaner stud and tighten to 70-95 inch lbs. (8-10 Nm). Tighten the four retaining screws.
- The rest of the assembly is in the reverse order of disassembly.
- Place the transmission in P or N .
- Allow the engine to operate until normal operating temperature is reached.
- Turn all accessories off.
- Shut the engine OFF . Restart the engine, run at 2000 rpm for 60 seconds in N and let the engine idle stabilized for 15 seconds before checking or adjusting the curb idle rpm.
- Have and assistant place the transmission in R and check/adjust the curb idle rpm. If adjustment is necessary, use the saddle bracket adjusting screw.
- Check/adjust the Throttle Position Sensor (TPS), refer to Fuel System .
CFI COMPONENT TESTS
Complete CFI system diagnosis requires the use of special test equipment. Have the system tested professionally.
Before beginning any component testing, always check the following:
High Pressure In-Tank Pump
Disconnect the electrical connector just forward of the fuel tank. Connect a voltmeter to the body wiring harness connector. Turn the key ON while watching the voltmeter. Voltage should rise to battery voltage, then return to zero after about 1 second. Momentarily turn the key to the START position. Voltage should rise to about 8 volts while cranking. If voltage is not specified, check electrical system.High Pressure In-Line & Low Pressure In-Tank Pumps
Disconnect the electrical connector at the fuel pumps. Connect a voltmeter to the body wiring harness connector. Turn the key ON while watching the voltmeter. The voltage should rise to battery voltage, then return to zero after about 1 second. If the voltage is not as specified, check the inertia switch and the electrical system. Connect an ohmmeter to the in-line pump wiring harness connector. If no continuity is present, check the continuity directly at the in-line pump terminals. If no continuity at the in-line pump terminals, replace the in-line pump. If continuity is present, service or replace the wiring harness.
Connect an ohmmeter across the body wiring harness connector. If continuity is present (about 5 ohms), the low pressure pump circuit is OK. If no continuity is present, remove the fuel tank and check for continuity at the in-tank pump flange terminals on top of the tank. If continuity is absent at the in-tank pump flange terminals, replace the assembly. If continuity is present at the in-tank pump but not in the harness connector, service or replace the wiring harness at the in-tank pump.Solenoid and Sensor Resistance Tests
All CFI components must be disconnected from the circuit before testing the resistance with a suitable ohmmeter. Replace any component whose measured resistance does not agree with the specifications chart. Shorting the wiring harness across a solenoid valve can burn out the circuitry in the ECA that control the solenoid valve actuator. Exercise caution when testing the solenoid valves to avoid accidental damage to ECA.