Fuel Metering System Component Description. Oldsmobile Intrigue 1999

For 1990-2009 cars only

Makes 🢒 Oldsmobile 🢒 1999 🢒 Intrigue 🢒 Engine 🢒 Engine Controls - 3.5L 🢒 Fuel Metering System Component Description

Basic System Operation

The fuel metering system starts with the fuel in the fuel tank. An electric fuel pump, located in the fuel tank with the gauge sending unit, pumps fuel to the fuel rail through an in-line fuel filter. The fuel pump is designed to provide fuel at a pressure above the pressure needed by the fuel injectors. A fuel pressure regulator in the fuel rail keeps fuel available to the fuel injectors at a constant pressure. Unused fuel is returned to the fuel tank by a separate pipe. For further information on the fuel tank, in-line filter, and fuel pipes. Refer to Fuel Supply Component Description .

Fuel Feed, Return, and EVAP Pipes - Engine Compartment

The fuel feed pipe delivers the fuel from the fuel tank to the fuel rail assembly. The fuel feed pipe carries excess fuel from the outlet port of the fuel rail back to the fuel tank. The canister purge pipe transfers fuel vapors to the charcoal canister.

Fuel Feed, Return, EVAP Pipes, and Canister - Chassis

The fuel feed, return, vacuum and EVAP pipes are assembled as a harness. Retaining clips hold the pipes together and provide a means for attaching the pipes to the vehicle. Quick-connect type fittings are used at the ends of the fuel feed and return and at the in-line fuel filter. They are described below. Sections of the pipes that are exposed to chafing, high temperature or vibration are protected with heat resistant rubber hose and/or coextruded conduit.

Nylon Fuel Pipes

Nylon fuel pipes are designed to perform the same function as the steel or rubber fuel pipes they replace. Nylon pipes are constructed to withstand maximum fuel system pressure, exposure to fuel additives, and changes in temperature. Both fuel feed and fuel return pipe size is 5/16 OD. The EVAP pipe from tank to canister size is 1/4 OD and from canister to engine is 5/16 OD. The vacuum signal pipe is 1/4 ID. Nylon fuel pipes are somewhat flexible and can be formed around gradual turns under the vehicle. However, if forced into sharp bends, nylon pipes will kink and restrict fuel flow. Also, once exposed to fuel, nylon pipes may become stiffer and more likely to kink if bent too far. Special care should be taken when working on a vehicle with nylon fuel pipes.

Caution: In order to Reduce the Risk of Fire and Personal Injury:

•	If nylon fuel pipes are nicked, scratched or damaged during installation, Do Not attempt to repair the sections of the nylon fuel pipes. Replace them.

•	When installing new fuel pipes, Do Not hammer directly on the fuel harness body clips as it may damage the nylon pipes resulting in a possible fuel leak.

•	Always cover nylon vapor pipes with a wet towel before using a torch near them. Also, never expose the vehicle to temperatures higher than 115°C (239°F) for more than one hour, or more than 90°C (194°F) for any extended period.

•

Before connecting fuel pipe fittings, always apply a few drops of clean engine oil to the male pipe ends. This will ensure proper reconnection and prevent a possible fuel leak. (During normal operation, the O-rings located in the female connector will swell and may prevent proper reconnection if not lubricated.)

Quick-Connect Fittings

Quick-connect type fittings provide a simplified means of installing and connecting fuel system components. There are two types of quick-connect fittings, each used at different locations in the fuel system. Each type consists of a unique female socket and a compatible male connector. O-rings, located inside the female socket, provide the fuel seal. Integral locking tabs or fingers hold the fittings together. The quick-connect fittings used at the fuel filter and other connections at the rear of the vehicle have hand releasable locking tabs. The fittings used at the engine fuel pipes have locking tabs that require a special tool to release.

Mass Air Flow (MAF) Sensor

The Mass Air Flow (MAF) sensor is located in the MAF sensor between the air snorkel and the throttle body. It senses the amount of air entering the intake manifold. This information is required by the PCM to control fuel and emissions.

The MAF sensor used on this vehicle is a hot wire type and is used to measure air flow rate (mass/unit time). The MAF sensor output is a variable frequency square wave based on air mass traveling through the sensor. A low frequency output signal from the MAF sensor indicates low air flow and high frequency indicates high air flow. The MAF sensor has two wires crossing the air stream through it. One senses ambient temperature and the other, the hot wire, is kept at a fixed temperature above the ambient temperature. The MAF sensor senses air flow by measuring the power necessary to keep the hot wire hot, which is proportional to air flow, and converts it to a frequency modulate output signal.

Accelerator Controls

The accelerator control system is cable-type. There are no linkage adjustments. Therefore, the specific accelerator control cable (3) must be used. The accelerator control (3) and cruise control (1) cables are attached to a retainer (2).

Throttle Body Unit


(1)	Idle Air Control Valve (IAC) Assembly O-Ring
(2)	Idle Air Control Valve Assembly
(3)	Idle Air Control Valve Attaching Screw
(4)	Throttle Position Sensor (TP) Attaching Screw
(5)	Throttle Position Sensor
(6)	Throttle Position Sensor O-Ring
(7)	Throttle Body Assembly

The throttle body has a throttle plate to control the amount of air delivered to the engine. The TP sensor, MAF sensor, and IAC valve are also mounted on the throttle body.

Vacuum ports located behind the throttle plate provide the vacuum signals needed by various components. Engine coolant is directed through a coolant cavity in the throttle body to warm the throttle valve and prevent icing.

Idle Air Control (IAC) Valve

The purpose of the Idle Air Control (IAC) valve is to control engine idle speed, while preventing stalls due to changes in engine load. The IAC valve, mounted in the throttle body, controls bypass air around the throttle plate. By moving a conical valve, known as a pintle, in (to decrease air flow) or out (to increase air flow), a controlled amount of air can move around the throttle plate. If RPM is too low, the PCM will retract the IAC pintle, resulting in more air being bypassed around the throttle plate to increase RPM. If RPM is too high, the PCM will extend the IAC pintle, allowing less air to be bypassed around the throttle plate, decreasing RPM.

The IAC pintle moves in small steps called counts.

During idle, the proper position of the IAC pintle is calculated by the PCM based on battery voltage, coolant temperature, engine load, and engine RPM. If the RPM drops below a specified value, and the throttle plate is closed (TP sensor voltage is between 0.20-0.74), the PCM senses a near stall condition. The PCM will then calculate a new IAC pintle position to prevent stalls.

If the IAC valve is disconnected and reconnected with the engine running, the idle RPM will be wrong. In this case, the IAC has to be reset.

The IAC resets when the key is cycled ON then OFF.

When servicing the IAC, it should only be disconnected or connected with the ignition OFF in order to keep from having to reset the IAC.

The position of the IAC pintle affects engine start up and the idle characteristics of the vehicle. If the IAC pintle is open fully, too much air will be allowed into the manifold. This results in high idle speed, along with possible hard starting and a lean air/fuel ratio. DTC P0507 may set. If the IAC pintle is stuck closed, too little air will be allowed in the manifold. This results in a low idle speed, along with possible hard starting and a rich air/fuel ratio. DTC P0506 may set. If the IAC pintle is stuck part way open, the idle may be high or low and will not respond to changes in engine load.

Throttle Position (TP) Sensor

The TP sensor is a potentiometer that is mounted on the throttle body and provides the PCM with information on throttle valve angle. The PCM provides a reference signal and a ground to the TP sensor and the sensor returns a signal voltage that changes with throttle valve angle. At closed throttle (close to 0°) the TP sensor output signal is low (below 1 volt) and at WOT (greater than 80°) the TP sensor output signal is high (above 4 volts). Because the TP sensor is not adjustable, the PCM must account for build tolerances that could affect the TP sensor output at closed throttle. The PCM uses a learning algorithm so that it can correct for variations.

The PCM uses TP information to modify fuel control based on throttle valve angle. For example, power enrichment occurs when the throttle angle approaches WOT. Acceleration enrichment occurs when the throttle angle increases rapidly (similar to an accelerator pump on a carburetor). A faulty TP sensor may cause various driveability conditions and should set a DTC.

Fuel Rail Assembly Identification

An eight digit identification number is stamped on the fuel rail assembly. The model identification number contains the Julian Date, the year, and the shift. Refer to this model identification number if servicing or part replacement is required.

Names of component parts will be found on the numbered list that accompanies the disassembled view.

Fuel Rail


(1)	Fuel Pressure Connection Cap
(2)	Fuel Pressure Core Assembly
(3)	Fuel Injector Retainer Clip
(4)	Fuel Injector Lower O-Ring
(5)	Fuel Injector Assembly
(6)	Fuel Injector Upper O-Ring
(7)	Regulator Seal Lower O-Ring
(8)	Regulator Assembly Filter
(9)	Regulator Seal Upper O-Ring
(10)	Back-Up Ring
(11)	Fuel Pressure Regulator Assembly
(12)	Regulator Retainer

The fuel rail design provides utilizes top-feed fuel injectors for fuel delivery. The fuel rail attaches to the intake manifold without the use of bolts.

The fuel rail is mounted to the top of the engine and distributes fuel to the six individual fuel injectors. Fuel is delivered to the fuel inlet tube of the fuel rail by the fuel pipes. The fuel then goes through the fuel rail to the fuel pressure regulator. The fuel pressure regulator maintains a constant fuel pressure at the fuel injectors. Fuel in excess of injector needs flows back through the pressure regulator assembly to the outlet port of the fuel rail. Fuel then flows through the fuel return pipe to the fuel tank to begin the cycle again. Remaining fuel is then returned to the fuel tank. Fuel pressure can be observed using a fuel pressure gauge at the fuel pressure gauge connection.

Fuel Pressure Regulator

The fuel pressure regulator is located in the fuel rail on the return side of the system.

The function of the regulator is to maintain a constant 300 kPa fuel pressure across the director spray plate under all operating conditions. The pressure regulator compensates for engine load by increasing fuel pressure as engine intake manifold vacuum drops. The pressure regulator is mounted on the fuel rail.

The regulator contains a vacuum chamber separated by a diaphragm relief valve assembly. The diaphragm has fuel on one side and engine manifold pressure (vacuum) on the other. A calibration spring is located in the vacuum chamber side. Fuel pressure is regulated as pressurized fuel, acting on the bottom side of the diaphragm working against the spring action on the top side. When the fuel diaphragm relief valve moves, opening and closing the orifice in the fuel chamber. This controls the amount of fuel returning to the fuel tank. Fuel rail pressure is controlled by the return spring calibration as well as engine vacuum acting on the top side of the diaphragm.

The cartridge regulator is serviced as a separate component.

If the fuel pressure is too low, poor performance and a DTC P0171, could result. If the pressure is too high, excessive odor and a DTC P0172, may result. Refer to Fuel System Pressure Test , for information on diagnosing fuel pressure conditions.

With the ignition On, and engine Off (zero vacuum), system fuel pressure at the pressure test connection should be 284 to 325 kPa (41 to 47 psi). If the pressure regulator supplies fuel pressure which is too low or too high, a driveability condition will result. With the engine running at idle and manifold vacuum applied to the regulator, system pressure will be 21 to 69 kPa (3 to 10 psi) less than the test specification.

Fuel Injector

The fuel injectors on this model are approximately half the size and weight of a traditional fuel injector and, have a simplified design that reduces the potential for contamination.

The fuel injectors deliver the fuel to the engine. The fuel injector is a solenoid operated device controlled by the PCM. The injector is provided a continuous supply of pressurized fuel. The PCM energizes the solenoid which opens a valve to allow fuel delivery. When the injector nozzle opens, the pressurized fuel is injected into the intake manifold, providing an atomized air fuel mixture for the engine. The fuel further atomizes as it enters the combustion chamber.

Engine RPM determines when an injector opens, the PCM, based on readings of coolant temperature, engine load, throttle position, and oxygen sensor voltage determines how long to leave the fuel injector open.

Excess fuel not used by the injectors passes through the fuel pressure regulator before being returned to the fuel tank.

A fuel injector which is stuck partly open will cause a loss of fuel pressure after engine shut down, causing long crank times to be noticed on some engines.

Fuel Pump Electrical Circuit

The PCM provides ignition positive voltage to control the fuel pump relay. The PCM has the ability to detect an electrical malfunction on the relay control circuit. When the ignition switch is first turned ON, the PCM energizes the fuel pump relay which applies power to the fuel pump. The fuel pump relay will remain ON as long as the engine is running or cranking and the PCM is receiving reference pulses. If no reference pulses are present, the PCM de-energizes the fuel pump relay within 2 seconds after the ignition is turned ON or the engine is stopped. With the engine stopped, the fuel pump can be turned ON by using the scan tool output controls function. If an electrical malfunction is detected, the PCM will set DTC P0230.

An inoperative fuel pump relay can result in a no start condition.

An inoperative fuel pump would cause a no start condition. A fuel pump which does not provide enough pressure can result in poor performance.

Powertrain Control Module (PCM)

The PCM receives data from various information sensors, determines the required fuel and idle speed values and then controls the IAC valve, six fuel injectors, and spark advance to maintain the optimum performance and driveability under all driving conditions. For more information on the PCM, refer to Powertrain Control Module Diagnosis .

The fuel pump relay allows the fuel pump to be energized by the PCM. When the ignition is first turned On, the PCM energizes the fuel pump relay for two seconds. This allows the fuel pump to run for two seconds and build up fuel pressure for cranking. The PCM then waits for ignition reference pulses from the Ignition Control Module (ICM). Once the PCM sees references pulses, the PCM energizes the relay to run the fuel pump.

A faulty fuel pump relay may cause long cranking times and should set a DTC.