Fuel Injection System - Multi-Port Chevrolet Camaro III рестайлинг

DESCRIPTION

The Port Fuel Injection (PFI) system is controlled by an on-board computer known as the Electronic Control Module (ECM). The ECM monitors engine operations and environmental conditions. The ECM output signals provide correct air/fuel ratio, ignition timing and idle speed.

Standard PFI systems feature simultaneous double-fire injection. Fuel rail, mounted to the intake manifold, provides fuel for the injectors. Fuel is constantly circulated through the rail during engine operation.

Injectors pulse once for each engine revolution, providing fuel directly to combustion chamber with precise timing. On Sequential Fuel Injection (SFI) models, injectors pulse sequentially in spark plug firing order. Differences between these systems are injector wiring and the ECM.

In all systems, constant fuel pressure is maintained to the injectors. Air/fuel ratio is adjusted by the time that injector stays open (pulse width). Various sensors provide information to the ECM to control pulse width. There are 2 major sub-systems; fuel system and electronic control system.

Note. Primary sub-systems affecting fuel system operation are covered in this article. Because of interrelated functions of Computer Command Control (CCC) system, refer to COMPUTER CONTROLS section for additional information.

FUEL SYSTEM

The fuel system provides a constant, pressurized supply of fuel to the injectors. Fuel system consists of throttle body, fuel tank, in-tank electric fuel pump, fuel pump relay, fuel pressure regulator, in-line fuel filter, fuel rail, injectors and Idle Air Control (IAC) valve.

ELECTRONIC CONTROL SYSTEM

Electronic control system monitors engine operating conditions, processes the information, and controls engine for optimum performance and minimum emissions.

Input signals are generated by the Engine Coolant Temperature (ECT) sensor, Mass Airflow (MAF) sensor, exhaust Oxygen (O2) sensor, Throttle Position Sensor (TPS), Power Steering Pressure Switch (PSPS), Park/Neutral switch, Vehicle Speed Sensor (VSS), Manifold Air Temperature (MAT) sensor and Manifold Absolute Pressure (MAP) sensor.

Some engines may use a combination of MAT and MAP sensors in place of MAF sensor. The MAT and MAP sensors are used to determine airflow. The ECM may also receive signals from starter solenoid during cranking mode, air conditioning selector switch and distributor.

FUEL CONTROL SYSTEM

Fuel control system contains an electric fuel pump, located in the fuel tank with gauge sending unit. Fuel is pumped to the fuel rail through an in-line fuel filter. Fuel pump provides fuel at a pressure exceeding fuel injector requirements.

Pressure regulator, mounted on the fuel rail, maintains a proper constant fuel pressure to the injectors. Pressure regulator increases the fuel pressure when engine vacuum decreases.

Unused fuel is returned to the fuel tank by a fuel return line. For correct fuel injector delivery at the ECM command, the fuel supply system maintains a constant pressure of approximately 36.0 psi (2.5 kg/cm 2 ) drop across the injectors.

The fuel pressure accumulator, used on some models, isolates fuel line noises. The fuel rail provides the upper mount for fuel injectors. Spring-loaded pressure tap may be used for testing fuel system.

Typical Port Fuel Injection System. Scheme 1

FUEL PUMP

Fuel is supplied by an in-tank positive displacement roller vane fuel pump. The pump supplies fuel through the in-line fuel filter to the fuel rail assembly. The pump is removed for service along with fuel gauge sending unit. (Scheme 2)

Once removed from tank, pump and sending unit are serviced separately. The pressure relief valve in the fuel pump, controls fuel pump maximum fuel pump pressure at 60-90 psi (4.2-6.3 kg/cm 2 ). Excess fuel flows through pressure regulator and returns to the tank.

The constant flow of cool fuel prevents fuel vapor bubbles. When ignition is turned on, fuel pump relay activates the fuel pump for 2 seconds to prime the injectors. If engine does not start within this time, the ECM deactivates fuel pump until engine starts.

After engine starts, the ECM closes the fuel pump relay, activating the fuel pump. As a back-up system to fuel pump relay, fuel pump can also be activated by an oil pressure switch. The oil pressure switch is normally open until oil pressure reaches approximately 4 psi (.28 kg/cm 2 ). If fuel pump relay fails, the oil pressure switch closes when oil pressure is obtained, operating the fuel pump. Inoperative fuel pump relay may result in extended cranking times.

Typical In-Tank Roller Vane Fuel Pump. Scheme 2

FUEL PRESSURE REGULATOR

Fuel pressure regulator is a diaphragm-operated relief valve with injector pressure on one side and manifold pressure on the other. (Scheme 3) Pressure regulator compensates for engine load by increasing fuel pressure when low manifold vacuum is experienced.

Fuel pressure is regulated when pump pressure acting on the bottom side of the diaphragm overcomes the spring force action on the top side. Diaphragm movement opens or closes the fuel chamber orifice, controlling the amount of returned fuel which maintains constant pressure at the injectors.

Sectional View of Fuel Pressure Regulator. Scheme 3

FUEL RAILS

Fuel rail assembly includes a fuel pressure regulator, individual high pressure fuel injectors and cold start injector. The injectors fit into individual sockets of base plate. Injectors are force fit into fuel rail opening. (Scheme 4) Retainer clip is pushed into its locked position. Some retainer clips must be rotated in the proper direction to lock.

Typical Fuel Rails for 2.8L, 5.0L & 5.7L Engines. Scheme 4

FUEL INJECTORS

The solenoid operated port fuel injector is controlled by the ECM. The injector consists of a valve body with a specially ground nozzle valve. The moveable armature is attached to the nozzle valve. Nozzle valve is held against nozzle body sealing seat by spring pressure.

Electric pulses generate a magnetic field in injector solenoid wiring. This draws the armature backward against spring pressure and lifts nozzle from the seat. Spring pressure forces the nozzle valve closed. (Scheme 5)

The ECM energizes the solenoid, opening the valve, allowing pressurized fuel to be injected. ECM obtains predetermined air/fuel ratio by controlling the injector energized time.

Fuel injector is installed in intake manifold at each cylinder. Injector sealing is provided with "O" ring seals. Lower "O" ring seals between injector and intake manifold. Upper "O" ring seals between injector and fuel rail. Replace "O" rings when injector is removed.

Each injector contains a wire connector. One wire supplies voltage from fuse panel. Second wire connects to ECM ground and controls injector pulse width.

Typical Fuel Injector. Scheme 5

Note. On Sequential Fuel Injection (SFI), wiring harness MUST be connected to the correct injector. One wire connects battery voltage to injectors. The ECM ground circuit for each injector is color coded differently for identification.

COLD START VALVE

The cold start valve provides additional vaporized fuel during cranking mode to improve cold engine start-up. This circuit is required due to not enough fuel for cold engine start.

The starter solenoid supplied circuit is activated only during cranking mode. A thermal switch provides a valve ground path when engine coolant temperature is below 95°F (35°C).

Thermal switch consists of a bi-metallic material which opens at specified coolant temperature. This bi-metallic material is also heated by the thermal switch winding. This allows the valve to remain on for 8 seconds at -5°F (-20°C) coolant temperature.

The thermal switch closed time varies with coolant temperature. As coolant temperature rises, cold start valve operation time decreases.

AIR INDUCTION SYSTEM

Air is drawn into the induction system through an air pick-up duct mounted in front of radiator support. This ensures intake air is lower temperature than engine compartment temperatures, resulting in denser air supply to combustion chambers.

Air intake duct provides turbulent free airflow for accurate measurement at the MAF sensor. Duct between MAF and throttle body must be air tight. Air entering behind the MAF sensor will not be measured, and cause a lean air/fuel ratio. Rubber boot between MAF sensor and throttle body prevents this air leakage.

THROTTLE BODY

Throttle body controls amount of air entering intake manifold. Mounted on the throttle body are the TPS and IAC valves. The TPS enables ECM to determine throttle position under all operating conditions.

Throttle body contains vacuum ports used to supply signals to various components. On some models, engine coolant is routed through bottom of throttle body to warm housing and prevent icing. (Scheme 6)

Exploded View of Typical Throttle Body. Scheme 6

IDLE AIR CONTROL

The Idle Air Control (IAC) valve controls engine idle speed during engine load changes to prevent stalling. Mounted in the throttle body, the IAC controls by-pass air around throttle valve. Movement of IAC conical valve inward toward the seat decreases airflow while movement away from the seat increases airflow around throttle plate.

The IAC valve moves in small steps called "COUNTS", and can be measured with test equipment plugged into the Assembly Line Diagnostic Link (ALDL). Increase of "COUNTS" indicates more air passing IAC valve.

Proper positioning of IAC valve at idle is determined by the ECM based on battery voltage, coolant temperature, engine load and engine RPM. Drop in engine speed below a specified RPM, with throttle plate closed, the ECM senses a near stall condition. The ECM then repositions IAC valve to prevent stalls.

Disconnecting and reconnecting of IAC valve with engine running will result in incorrect idle RPM. The IAC valve must be reset. On 2.0L, the IAC is reset when vehicle is operated over 35 MPH. On all others, IAC resets when ignition switch is turned from the "ON" to the "OFF" position. When servicing IAC, disconnect or connect only with ignition off to prevent resetting of IAC.

The IAC valve affects only the idle system. If valve is stuck fully open, excessive airflow into the manifold creates an high idle speed. Valves stuck closed allows insufficient airflow, resulting in low idle speed. Different design IAC valves are used. Ensure proper design valve is used during replacement.

Speed Density

On models equipped with MAP and MAT sensors, the speed density is used to compute the airflow rate. Manifold pressure and temperature are used to calculate the airflow rate to the ECM. The MAP sensor responds to manifold vacuum changes due to engine load and speed changes.

The ECM sends a volt signal to the MAP sensor. Manifold pressure changes result in resistance changes of MAP sensor. By monitoring MAP sensor output voltage, the ECM determines manifold pressure. If MAP sensor fails, the ECM will apply a fixed MAP value and use the TPS to control fuel.

Mass Airflow

Air mass entering the induction system is measured by the MAF sensor. A ceramic resistor is used to measure incoming air temperature. Incoming air cools the sensing element. Measurement of electrical power to maintain the MAF sensor ceramic resistor at 165°F (75°C) above the incoming air temperature determines the air mass. (Scheme 7)and (Scheme 8).

The electrical power requirement is measured and converted to a digital signal (30-150 Hz), which is then sent to the ECM. This is then used to determine engine load.

Using calculations of mass airflow, engine temperature and RPM, the ECM calculates the fuel requirement to provide a proper air/fuel ratio of 14.7:1.

Some MAF units are the Bosch hot wire type. This type contains a sensing wire. Current is supplied to maintain a calibrated temperature. Current varies with amount of airflow. Current changes are processed by the ECM to provide proper air/fuel ratio.

The sensing wire contamination is prevented by heating sensing wire to 1000°F (538°C) after engine shutdown. This burn off cycle is controlled by the ECM. If burn off cycle did not occur, the Service Engine Soon light will activate and stay on after next engine start.

Exploded View of Mass Airflow Sensor. Scheme 7

Scheme 8

PRELIMINARY CHECKS

The following should be checked prior to trouble shooting fuel system

1. Ensure Service Engine Soon light is operable.
2. Check that no trouble codes are stored.
3. ECM grounds are clean and tight.
4. Check for faulty vacuum hoses.
5. Check for vacuum leaks at throttle body and intake manifold.
6. Check ignition system for faulty components.
7. Inspect wiring connections and condition.

FUEL PRESSURE RELIEF

1. Fuel system is under pressure. Pressure must be relieved prior to servicing fuel system. Fuel pressure may be relieved by 2 different methods.
2. One method is to disconnect fuel pump at rear body connector. Start engine and allow to run until it stops. Operate starter for 3 seconds to remove remaining fuel from fuel lines. Reconnect fuel pump once repair is completed.
3. The other method is to install Fuel Pressure Gauge (J-34730-1) on fuel pressure connection. Wrap shop towel around pressure connection when installing fuel pressure gauge to absorb fuel leakage.
4. Install gauge bleed hose in container. Open bleed valve to bleed fuel pressure.

FUEL SYSTEM DIAGNOSIS

See appropriate A-7 FUEL SYSTEM DIAGNOSIS CHART in COMPUTER CONTROLS section.

Hard Start

1. If engine starts but then dies immediately, see appropriate ENGINE CRANKS BUT WILL NOT RUN diagnostic chart in COMPUTERIZED ENGINE CONTROL section. Check for sticking or binding TPS.
2. Check for high TPS voltage with throttle closed. Voltage should be less than .7 volts. Check for high resistance in coolant sensor circuit or coolant sensor.
3. Check fuel pressure and fuel pump relay. See appropriate A-7 FUEL SYSTEM DIAGNOSIS CHART in COMPUTER CONTROLS section. Check for contaminated fuel. Check in-tank fuel pump check valve operation.
4. If problem exists in cold weather only, check cold start valve operation. Check fuel evaporation system. Check EGR operation. Check ignition system.
5. Check spark plug condition. On 2.8L VIN S, 5.0L and 5.7L, if engine starts and immediately stalls, disconnect distributor by-pass line. If engine starts and runs okay, replace pick-up coil. If engine starts and then stalls, disconnect MAF sensor (if equipped). Replace MAF sensor if engine runs and sensor connections are okay.

Hesitation, Sag, Stumble

1. Check fuel pressure. See appropriate A-7 FUEL SYSTEM DIAGNOSIS CHART in COMPUTERIZED ENGINE CONTROL section. Check for contaminated fuel. Check for sticking or binding TPS.
2. Check PROM or MEM-CAL for proper application. Check spark plug condition. Check vacuum hose to MAP sensor for damage. Verify alternator output voltage is between 9 and 16 volts. Repair as necessary.
3. Check for air leak between MAF sensor and throttle body. Check canister purge system and EGR for proper operation. Check MAP or MAF sensor. Check ignition timing. Ensure engine is operating at proper temperature.
4. Check HEI ground circuit. Perform injector balance test. See appropriate C-2A INJECTOR BALANCE TEST in COMPUTERIZED ENGINE CONTROL section.

Rough, Unstable Idle

1. Check for sticking or binding TPS or throttle linkage. Check idle speed and IAC system. See CODE 35 CHART in COMPUTERIZED ENGINE CONTROL section.
2. Verify alternator output voltage is between 9 and 16 volts. Repair as necessary. Check P/N switch circuit (if equipped). Check ECM ground circuits. Check EGR system and PCV valve operation.
3. Perform injector balance test. See appropriate C-2A INJECTOR BALANCE TEST in COMPUTERIZED ENGINE CONTROL section. Check ignition system and ignition timing. Check fuel evaporative system. Ensure battery cables and ground straps are clean and tight.
4. Check A/C input to ECM. Check for vacuum leaks. Check for loose or damaged air duct between MAF sensor and throttle body. On 2.8L VIN S, 5.0L and 5.7L, check Air Injection Reaction (AIR) system. No air should exist at ports during closed loop operation.
5. On all models, inspect O2 sensor for contamination from fuel. Sensor is defective if coated with a White powdery coating. Disconnect MAF sensor. Replace sensor if condition is corrected.
6. Check for fuel in pressure regulator hose. Replace pressure regulator if fuel exists. Check cylinder compression.

Cuts Out, Misses

1. Disconnect IAC motor. Start engine. Using insulated pliers, remove one spark plug at a time and note RPM. If RPM drops within 50 RPM on all cylinders, proceed to ROUGH, UNSTABLE IDLE symptom in this article.
2. Check ignition system and cylinder compression if no RPM change was noted or exceeded 50 RPM. Repair as necessary.
3. Disconnect all injector wiring connectors. Install Injector Test Light (J034730-2) between connector terminals. Note light while cranking. Test light should blink during cranking. Check injector drive circuit if light fails to blink.
4. Check for restricted fuel filter or fuel contamination. Check fuel pressure. See appropriate A-7 FUEL SYSTEM DIAGNOSIS CHART in COMPUTERIZED ENGINE CONTROL section.
5. Perform injector balance. See appropriate C-2A INJECTOR BALANCE TEST in COMPUTERIZED ENGINE CONTROL section. Check ignition system. Check for worn or damaged engine components.

Detonation

1. Check for overheating problem. Check ignition timing. Check EGR operation. Check transmission Torque Converter Clutch (TCC) and Electronic Spark Control (ESC) operation. Check for improper fuel octane rating.
2. Check fuel pressure. See appropriate A-7 FUEL SYSTEM DIAGNOSIS CHART in COMPUTERIZED ENGINE CONTROL section. Check PROM or MEM-CAL for proper application. Check P/N switch input to ECM (if equipped).

Surges And/Or Chuggle

1. Check for loose or leaking air duct between MAF sensor and throttle body. Verify alternator output is between 9 and 16 volts. Repair or replace as necessary.
2. Check EGR filter condition and EGR operation. Check vacuum hoses for damage or leaks. Check for restricted in-line fuel filter. Check fuel pressure. See appropriate A-7 FUEL SYSTEM DIAGNOSIS CHART in COMPUTERIZED ENGINE CONTROL section.
3. Inspect O2 sensor for contamination from fuel. Sensor is defective if coated with a White powdery coating. Check ignition timing and spark plug condition.

Lack Of Power, Sluggish Or Spongy

1. Check air filter. Check for loose or leaking air duct between MAF sensor and throttle body. Check ignition timing. Check for fuel contamination, or restricted fuel filter.
2. Check fuel pressure. See appropriate A-7 FUEL SYSTEM DIAGNOSIS CHART in COMPUTERIZED ENGINE CONTROL section. Check ECM ground circuits. Check EGR operation. Check for restricted exhaust system.
3. Verify alternator output is between 9 and 16 volts. Repair or replace as necessary. Check ignition system. Check engine for worn internal components.
4. Check A/C operation. See appropriate C-10 A/C CLUTCH CONTROL CIRCUIT DIAGNOSIS CHART in COMPUTERIZED ENGINE CONTROL section.

Backfire

1. Check for loose wiring connector or air duct at MAF sensor. Check EGR valve mounting gasket or faulty valve operation. Check ignition timing and ignition system.
2. Check fuel system. See appropriate A-7 FUEL SYSTEM DIAGNOSIS CHART in COMPUTERIZED ENGINE CONTROL section. Perform injector balance test. See appropriate C-2A INJECTOR BALANCE TEST in COMPUTERIZED ENGINE CONTROL article. Check cylinder compression.

Poor Fuel Economy

1. Check air filter. Check fuel pressure. See appropriate A-7 FUEL SYSTEM DIAGNOSIS CHART in COMPUTERIZED ENGINE CONTROL section. Check ignition system and ignition timing.
2. Verify engine reaches normal operating temperature. Check TCC operation. Check exhaust system for restrictions. Check induction system and crankcase for air leaks. Check for vacuum leaks.

Dieseling

Check injector for leakage. See appropriate A-7 FUEL SYSTEM DIAGNOSIS CHART in COMPUTERIZED ENGINE CONTROL section.

Excessive Exhaust Emissions Or Odors

1. Check fuel pressure. See appropriate A-7 FUEL SYSTEM DIAGNOSIS CHART in COMPUTERIZED ENGINE CONTROL section. Check ignition timing. Check fuel evaporative and PCV systems.
2. Perform injector balance. See appropriate C-2A INJECTOR BALANCE TEST in COMPUTERIZED ENGINE CONTROL section. Check catalytic converter for lead contamination. Check for vacuum leaks. Verify engine is operating at normal operating temperature.

REMOVAL & INSTALLATION

Removal (2.0L, 3.0L & 3.8L)

1. Relieve fuel pressure. See «FUEL PRESSURE RELIEF»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port__fuel-pressure-relief) under TROUBLE SHOOTING in this article. Turn ignition off. Disconnect wiring connectors from injectors. Disconnect and plug hoses to fuel rail.
2. Remove fuel rail retaining bolts. Remove injector-to-fuel rail retaining clip (if used). Separate fuel rail from injectors. Remove injectors. (Scheme 9)

View Of 2.0L, 3.0L & 3.8L Fuel Rail Assembly. Scheme 9

Note. If injector is replaced, ensure replacement injector contains same Part No. as that removed.

Installation

Coat new "O" rings with oil. Install "O" rings on injectors. Reverse removal procedures. Tighten fuel rail retaining bolts to specification. See TORQUE SPECIFICATIONS table at end of article.

Removal (2.3L)

1. Relieve fuel pressure. See «FUEL PRESSURE RELIEF»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port__fuel-pressure-relief) under TROUBLE SHOOTING in this article. Remove crankcase ventilation oil/separator.
2. Remove fuel lines from fuel rail. Remove vacuum line at pressure regulator. Disconnect wiring connector while pushing inward on connector. Remove fuel rail retaining bolts. Remove fuel rail. (Scheme 10)
3. Remove injector-to-fuel rail retaining clip. Remove injector from fuel rail. Remove injector "O" rings.

View Of 2.3L Fuel Rail Assembly. Scheme 10

Lubricate injector "O" rings with oil. Install injector-to-fuel rail retaining clip with open end facing injector electrical connection. Reverse removal procedures. Tighten fuel rail retaining bolts.

Scheme 11

1. Disconnect negative battery cable. Upper plenum of intake manifold requires removal. Disconnect and mark vacuum lines. On 2.8L, remove EGR-to-intake manifold retaining bolts. Some models use an EGR pipe which requires removal at EGR base.
2. On all models, remove throttle cable bracket bolts. Disconnect cables and electrical wiring connections from throttle body. Remove throttle body from intake manifold. Remove upper plenum bolts.
3. On 5.0L and 5.7L, remove upper plenum-to-runner bolts. Remove plenum and gasket. (Scheme 11) (Scheme 11): View Of 2.8L, 5.0L & 5.7L Fuel Rail Assembly
4. Disconnect vacuum hose to pressure regulator. Relieve fuel pressure. See «FUEL PRESSURE RELIEF»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port__fuel-pressure-relief) under TROUBLE SHOOTING in this article. Disconnect cold start valve line.
5. On 5.0L and 5.7L, remove runners and cold start valve. Disconnect fuel lines from fuel rail. On all models, with ignition off, disconnect electrical connections from injectors.
6. Remove fuel rail retaining bolts. Remove fuel rail and injectors. On 2.8L, separate injector retaining clip ends and remove clip. On 5.0L and 5.7L, rotate injector retaining clip to unlock position.
7. On all models, remove injectors from fuel rail. Remove "O" rings from injectors.

Coat new "O" rings with oil. Install "O" rings on injectors. Reverse removal procedures. Tighten bolts to specification. See TORQUE SPECIFICATIONS table at end of article.

IDLE AIR CONTROL VALVE

Removal (2.3L & 2.8L VIN 9 & W)

1. Remove electrical connector from IAC valve. Remove IAC valve and gasket or "O" ring. IAC valve screws into housing on the 2.8L (VIN 9) and retaining screws are used on the 2.3L and 2.8L (VIN W).
2. DO NOT extend or retract pintle by hand. Pintle should only be moved electrically. Failure to do so will damage IAC valve. DO NOT remove thread sealant from 2.8L (VIN 9) IAC valve.

Install new "O" ring or gasket on valve. Coat "O" ring with oil. Install IAC valve. Tighten IAC valve on 2.8L (VIN 9) to 13 ft. lbs. (18 N.m). On all others, tighten retaining screws to 30 INCH lbs. (3.39 N.m). Install electrical connection. The IAC resets when ignition switch is turned from the "ON" to the "OFF" position.

Removal (All Others)

Remove electrical connection. Remove IAC valve from housing.

Scheme 12

1. Prior to installing new IAC valve, measure extended distance of the valve. (Scheme 12) Measurement should be taken from valve housing flange to end of cone. If cone extends beyond specification, valve damage will occur when installed.
2. Distance must not exceed more than 1 1/8" (28 mm). IAC must be retracted to within specification. On all models except the "3800" 3.8L (VIN C), determine if IAC valve is Type I or Type II. Type I contains a collar at electrical terminal and Type II does not. (Scheme 12) The "3800" 3.8L (VIN C) uses only Type I. (Scheme 12): IAC Valve Identification
3. To retract Type I, exert firm finger pressure on valve while moving pintle side-to-side. To retract Type II, compress retaining spring and turn valve clockwise inward. Reposition spring so straight portion aligns with valve flat surfaces.
4. Install IAC valve and gasket. Tighten to 13 ft. lbs. (18 N.m). On "3800" 3.8L (VIN C), tighten retaining screws to 18 INCH lbs. (2 N.m). Install electrical connection. On 2.0L the IAC resets when vehicle is operated above 35 MPH. On all others, the IAC resets when ignition switch is turned from the "ON" to "OFF" position.

OXYGEN SENSOR

Removal

Disconnect negative battery cable. Disconnect electrical lead from O2 sensor. Sensor may be difficult to remove when engine temperature is below 120°F (48°C). Remove O2 sensor.

1. Coat O2 sensor threads with Anti-Seize Compound (5613695) prior to installation. New sensors already contain anti-seize compound.
2. Install sensor and tighten to 30 ft. lbs. (41 N.m). Install electrical connector.

Disconnect electrical connection from TPS. Remove TPS retaining screws. Remove TPS sensor.

1. With throttle valve in closed position, install TPS on throttle body. Ensure TPS lever engages with drive lever on throttle shaft. Install retaining screws and electrical connection.
2. On 2.0L and 2.8L (VIN 9) models, tighten screws. No adjustment is required. On all other models, adjust TPS to specification and tighten retaining screws. See THROTTLE POSITION SENSOR under «ADJUSTMENTS»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port__adjustments) in this article.

1. Remove air inlet ducts. Disconnect and mark electrical connections and vacuum hoses from throttle body. Disconnect control cables from throttle body.
2. Drain cooling system. Remove coolant hoses. Remove throttle body retaining bolts. Remove throttle body and gasket.

Note. Identification number is stamped on throttle body near coolant cover. Identification number must be used for ordering replacement components.

1. Reverse removal procedures using new gasket. Tighten retaining bolts to specification. See «TORQUE SPECIFICATIONS»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port) table at end of article. Fill cooling system.
2. If IAC was removed, ensure of proper setting prior to installation. See «IDLE AIR CONTROL VALVE»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port__idle-air-control-valve) under REMOVAL & INSTALLATION in this article. Adjust idle speed and TPS (if removed). See «ADJUSTMENTS»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port__adjustments) in this article.

Removal & Installation (2.0L & 2.3L)

1. Relieve fuel pressure. See «FUEL PRESSURE RELIEF»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port__fuel-pressure-relief) in this article. On 2.0L, disconnect pressure regulator-to-fuel rail hose. On 2.3L, remove fuel rail. See «FUEL RAIL & INJECTORS»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port) under REMOVAL & INSTALLATION in this article.
2. On all models, remove pressure regulator retaining bolts. Remove pressure regulator from fuel rail. On 2.3L, remove pressure regulator retainer and seal from fuel rail.

On 2.3L, lubricate fuel rail seal with oil and install in regulator. On all models, reverse removal procedures. Tighten bolts to specification. See TORQUE SPECIFICATIONS table at end of article.

Removal (2.8L VIN W)

1. Relieve fuel pressure. See «FUEL PRESSURE RELIEF»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port__fuel-pressure-relief) in this article. Remove fuel rails. See «FUEL RAIL & INJECTORS»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port) under REMOVAL & INSTALLATION in this article.
2. Remove inlet and outlet fuel fittings and gaskets. Remove pressure regulator-to-bracket retaining bolts. Separate fuel rails from pressure regulator.
3. Remove pressure regulator base-to-fuel rail connector tubes from pressure regulator.

1. Lubricate new "O" rings with oil. Install fuel return "O" rings on fuel rails. Return "O" rings are larger diameter than connector tube "O" rings.
2. Reverse removal procedures for remaining components. Tighten bolts to specification.

Removal (5.0L & 5.7L)

1. Relieve fuel pressure. See «FUEL PRESSURE RELIEF»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port__fuel-pressure-relief) in this article. Remove fuel rails. See «FUEL RAIL & INJECTORS»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port) under REMOVAL & INSTALLATION in this article.
2. Remove front crossover tube retainer on right fuel rail. Remove rear crossover tube retainer at pressure regulator on right fuel rail. Separate fuel rail assemblies.
3. Remove pressure regulator bracket-to-fuel rail bolt. Remove bracket to regulator base bolt. Remove bracket. Remove fuel outlet tube-to-right fuel rail bolt. Remove base-to-right fuel rail bolt.
4. Remove pressure regulator assembly from fuel rail. Rotate pressure regulator and remove from outlet tube. Remove base-to-fuel rail connector tube. Remove "O" rings from connector tube, outlet tube, and crossover tubes.

Install new "O" rings and lubricate with oil. Reverse removal procedures. Tighten retaining bolts to specification. See TORQUE SPECIFICATIONS table at end of article.

Removal & Installation (Except Corvette)

1. Disconnect negative battery cable. Relieve fuel pressure. See «FUEL PRESSURE RELIEF»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port__fuel-pressure-relief) in this article. Remove filler neck. Lower fuel tank. Disconnect fuel lines and electrical connection.
2. Remove fuel level sending unit and pump retaining bolts or cam lock ring. Lift assembly from fuel tank and remove fuel pump from sending unit.
3. Pull fuel pump upward while pulling outward away from bottom support. Use care not to damage rubber insulator and strainer. Reverse removal procedures for installation using new "O" ring gasket.

Removal (Corvette)

1. Relieve fuel system pressure. Remove fuse marked "Fuel Pump" from fuse block in passenger compartment. Crank engine. Engine will start and run until fuel in line is exhausted. When engine stops, engage starter again for 3 seconds to ensure engine will not start.
2. Remove battery ground cable. Remove fuel cap, fuel tank filler door. Remove filler neck housing and disconnect drain hose. Remove screws attaching fuel meter and pump assembly to tank. Disconnect fuel hoses, vapor hose and electrical connector from fuel meter and pump assembly. Pull pump up into pulsator while pulling outward away from bottom support. Remove pump.

Reverse removal procedure, using new gasket.

ADJUSTMENTS

Note. For all on-vehicle adjustments not listed, see appropriate TUNE-UP article in this section.

MINIMUM IDLE SPEED

Note. Adjustment should be necessary only when throttle body or throttle body components have been replaced. Perform adjustment with engine at normal operating temperature.

2.0L & 2.8L (VIN 9)

Turn ignition on. Ground diagnostic terminal. Wait at least 30 seconds. Disconnect IAC. Start engine and note idle speed. If idle speed exceeds specification listed on Emissions Label for 2.0L or 750-850 RPM on 2.8L, check and repair vacuum leaks. No further information is available for either application.

2.3L

1. Apply parking brakes. Install "Scan" tool. Start engine and operate to normal operating temperature. Ensure engine enters closed loop. On A/T applications, shift into Drive then back to Neutral.
2. Ensure all accessories are off. Ensure no input is being received from power steering switch. See appropriate POWER STEERING PRESSURE SWITCH CHART C-1E in COMPUTERIZED ENGINE CONTROL section. Allow idle to stabilize.
3. Using "Scan" tool, note "COUNT" reading. Adjustment is correct if "COUNT" reading ranges between 5 and 45. If "COUNT" is low, check for vacuum leaks.
4. If "COUNT" exceeds specified range, remove inlet duct at throttle body and clean contamination from inside of throttle body. If "COUNT" reading still is not within specified range, throttle stop screw requires adjustment.
5. Using awl, pierce throttle stop screw plug and remove. Back stop screw outward until air gap exists between stop screw and throttle lever. Turn stop screw inward until it just contacts throttle lever.
6. Turn stop screw inward an additional 1 1/2 turns. Recheck "COUNT" reading. Rotate stop screw to increase throttle plate opening to lower "COUNT" reading or decrease opening to increase "COUNT" reading. Adjust TPS once reading is correct. See THROTTLE POSITION SENSOR under «ADJUSTMENTS»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port__adjustments) in this article.

Note. Following procedures does not apply to 3.8L "3800" (VIN C). No information was available.

2.8L (VIN S & W), 3.0L & 3.8L

1. Apply parking brakes. Ground diagnostic test lead with IAC motor connected. Pierce idle stop screw plug with an awl, and remove plug. Turn ignition on. DO NOT start engine.
2. Wait at least 45 seconds, allowing IAC to extend. Turn ignition on. Disconnect IAC electrical connector. Remove ground from diagnostic lead and start engine.
3. Allow engine to enter closed loop. Adjust minimum idle speed screw to obtain correct idle speed. See «IDLE SPEED SPECIFICATIONS»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port) table. Turn ignition off.
4. Reconnect IAC connector. Check and adjust TPS. See THROTTLE POSITION SENSOR under «ADJUSTMENTS»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port__adjustments) in this article.

IDLE SPEED SPECIFICATIONS

5.0L & 5.7L

1. Pierce idle stop screw plug with an awl, and remove plug. With IAC motor connected, ground diagnostic lead.
2. Turn ignition on. DO NOT start engine. Wait at least 30 seconds. Disconnect IAC electrical connector. Disconnect distributor "Set-Timing" connector.
3. On Corvette models, "Set-Timing" connector is located at left front of dash panel near the brake master cylinder. On Camaro models, "Set-Timing" connector is located at right rear of engine compartment taped to wiring harness. On both models the "Set-Timing" wire is a Tan/Blk wire.
4. Start engine and allow to enter closed loop. Remove ground from diagnostic connector. Adjust minimum idle speed screw to obtain correct idle speed. See «IDLE SPEED SPECIFICATIONS»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port) table. Turn ignition off.
5. Reconnect IAC connector. Check and adjust TPS. See THROTTLE POSITION SENSOR under «ADJUSTMENTS»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port__adjustments) in this article.

Note. Anytime minimum idle speed is adjusted, the Throttle Position Sensor (TPS) must be readjusted.

THROTTLE POSITION SENSOR (TPS)

Note. Throttle position sensor on 2.0L and 2.8L (VIN 9) are not adjustable.

1. Install "Scan" tool and select TPS. With ignition switch in "ON" position, adjust TPS to specification. See «TPS SPECIFICATIONS»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port) table. Adjust TPS output voltage in closed throttle position.
2. Tighten screws to specification. See «TORQUE SPECIFICATIONS»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port) table. Recheck voltage readings.

TPS SPECIFICATIONS

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

1988 Grand Am & Sunbird 2.0L Fuel Injection Wiring Diagram. Scheme 13

1988 Calais & Grand Am 2.3L Fuel Injection Wiring Diagram. Scheme 14

1988 Skylark 2.3L Fuel Injection Wiring Diagram. Scheme 15

1988 Camaro & Firebird 2.8L Fuel Injection Wiring Diagram. Scheme 16

1988 Regal FWD 2.8L Fuel Injection Wiring Diagram. Scheme 17

1988 Cutlass Supreme FWD 2.8L Fuel Injection Wiring Diagram. Scheme 18

1988 Cavalier 2.8L Fuel Injection Wiring Diagram. Scheme 19

1988 Beretta & Corsica 2.8L Fuel Injection Wiring Diagram. Scheme 20

Celebrity, Century, Cutlass Ciera & 6000 2.8L Wiring Diagram. Scheme 21

1988 Cimarron 2.8L Fuel Injection Wiring Diagram. Scheme 22

1988 Fiero 2.8L Fuel Injection Wiring Diagram. Scheme 23

1988 Calais & Skylark 3.0L Fuel Injection Wiring Diagram. Scheme 24

1988 Century & Cutlass Ciera 3.8L FI Wiring Diagram. Scheme 25

Bonneville, 88, LeSabre & 98 3.8L FI Wiring Diagram. Scheme 26

Bonneville & Electra 3.8L "3800" FI Wiring Diagram. Scheme 27

Camaro & Firebird 5.0 & 5.7L Fuel Injection Wiring Diagram. Scheme 28

1988 Corvette 5.7L Fuel Injection Wiring Diagram. Scheme 29

See also:
• FUEL PRESSURE RELIEF
• TORQUE SPECIFICATIONS
• ADJUSTMENTS
• IDLE AIR CONTROL VALVE