BMW 3 Series Service Manual (E39)

130-12

Fuel Injection

-Disconnect intake air boot from throttle housing. Unbolt throttle housing and lay aside. It is not necessary to disconnect throttle cable or electrical harness connectors from throttle housing.

-Remove electrical harness connector from IAT sensor.

-Unclip temperature sensor and remove from intake manifold.

-Installation is reverse of removal. Use a new gasket at throttle housing.

Throttle position sensor (TPS), testing and replacing

4 The throttle position sensor (arrow) is located on top of the throttle valve housing and provides the ECM with a voltage value that represents throttle position (angle) and rate of movement.

TheTPS is non-adjustable. If the throttle position sensor is replaced, the previous 'learned'TPS settings must be cleared from the ECM using a BMW-compatible scan tool.

If the throttle position sensor signal is defective, afault code is stored and the MILis illuminated when OBD IIfault criteria are exceeded. The ECM still operates the engine using the mass air flow (MAF)sensor and engine rpm inputs.

-Check throttle position sensor function by disconnecting harness connector and checking continuity across terminals. If test results are incorrect, replacethrottle position sensor. The sensor is non-adjustable.

sureCAUTION- OFF

Be ignition is before disconnectingor reconnecting DMEsvstem components.

130-13

Fuel Injection I

< Unplug harness connector (arrow) from sensor.

CAUTION-

Be sure ignition is OFFbeforedisconnectingor reconnecting DMEsystem components.

NOTE-

Do not confuse the throttle position sensor on the main Nirottle body with the throttle position switch on the secondary throttle body, where applicable.

-Remove two mounting screws holding sensor to throttle housing.

-Installation is reverse of removal. Clear adaptation settings from ECM using BMW-compatible scan tool.

NOTE-

Poor idle quality may be noticeable for a periodif the adaptation settings are not cleared after installing new TPS.

ldle speed control valve, checking and replacing

The idle speed control valve regulates idle speed by redirectinq airaround the throttlevalve.The idlespeed control valve is mounted on the underside of the intake manifold adjacent to the dipstick tube bracket. Accessing the valve is best accomplished by first removing the air filter housing and the throttle body assembly.

The valve issupplied with batteryvoltagefromthe ECM relay. The idle speed control valve incorporates a two-coil rotary actuator. The ground sides of each coil are pulsed sirnultaneously by the ECM. The duty cycle of each circuit is varied to achieve the required idle speed.

Afaulty ldle speed control valve sets afault code and the MIL is illuminated when OED II fault criteria are exceeded.

Before checking the idle speed control valve, confirmthat the throttle position sensor is working correctly.

-With engine running, check that idle speed control valve is buzzing.

-Turn on AIC system or shift transmission into drive. ldle should remain steady or increase slightly.

Fuel injectors, checking and replacing

The fuel injectors are electronically controlled solenoid valves that provide precisely metered and atomized fuel into the engine intake ports.

The injectors receive voltage from the ECM relay. The ECM controls the opening by activating the ground circuit forthe injector valve solenoids. The ECM varies the duration (in milliseconds) of "opening" time to regulate the airlfuel ratio.

For a quick check of the injectors, run the engine and touch each injector with a screwdriver or stethoscope. You should feel a vibration or hear a buzzing

Remove fuel injection harness from injectors by unclipping locking clip at each injector. Lift harness off injectors.

CAUJ I O G

Besure ignitionis OFFbeforedisconnectingor reconnecting DME system components.

Use a multimeter to test injector coil resistance between injector terminals.

Disconnect negative (-) battery cable

C A U T I O G

Prior to disconnectingthe battery, readthe battery disconnection cautionsgiven in001 General Warnings and Cautions.

4 Remove plastic trim plugs (arrows) and fasteners, then re. move cover from above fuel injectors.

-Disconnect vacuum line from fuel pressure regulator.

-Remove wiring harness duct mounting fasteners.

IFuel Injection

Release injector locking clips at each injector and pry injector wiring duct up off injectors.

Clamp off fuel supply line and fuel return line at end of fuel rail. Disconnect fuel supply fuel return lines from fuel rail.

WARNING-

Clamp off the fuel lines and then wrap a clean shop towel around the lines before removingthem. Residualfuelpressure ispresent in the lines.

-Remove fuel rail mounting fasteners

-Pull up on fuel rail and remove individual injectors by removing injector retaining clip and pulling injector from rail.

-Installation is reverse of removal. Fit new O-rings when installing injectors. For ease of installation, lightly lubricate injector O-ring with SAE9O gear lube.

Tightening torque

Evaporative emissions, overview

On E39 MS 41.I cars, the evaporative emissions system is combined with the tank ventilation system. The evaporative system is monitored by the ECM for correct purge operation and leak detection.

The carbon (purge) canister is purged using engine vacuum via the purgevalve.The purgevalve (located nextto the mass airflow sensor) is ECM controlled and regulates the purge flow into the intake manifold. The valve is powered open and closed by an internal spring.

Ifthe evaporative emission valve circuit is faulty, a fault code is set and the MIL is illuminated when OBD II fault criteria are exceeded. If the valve is mechanically faulty, poor driveability may result and a mixture adaptation fault is stored in the ECM.

The leak diagnosis pump (LDP) is activated by the ECM and pressurizes the fuel tank and evaporative system as apart of theOED I1 leakdetection monitor. Ifthe LDP orthe LDP circuit is defective, afault code is set and the MIL is illuminated when OBD I1 fault criteria are exceeded. The LDP is mounted the left rear wheel well behind the fender liner.

Fuel Injection 1

NOTE-

The 1998 5281'with MS 41.1 requires a barometric pressure sensor input signal for activation of the LDPcheck. This sensor is located on the passenger side strut tower f o ~ l a r dof ABS/ASC hydraulic unit.

Evaporative emissions

1.ECM

2.Purge valve

3.Leak detection pump (LDP) (in lefl rear wheel housing)

4.Filter

5.Liquid vapor separator

6.Purge canister

7.Fuel tank

Secondary air injection, overview

The secondary air systempumpsambientair intothe exhaust stream afler a cold engine start to reducethe warm uptime of the catalytic converters and to reduces HC and CO emissions. The ECM controls and monitors the secondary air injection system. The secondary air pump operates at a start temperature of between 10°C(50°F) and40°C (104°F)and continues to operate for a maximumof 2 minutes at idle speed.

The electric air pump draws in ambient air and supplies it to the divertervalve. The vacuum ventvalve (solenoid)switches vacuum to open the divertervalve when activated by the ECM. Once opened, the diverter valve allows air to be pumped into the exhaust stream.

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Table b. Siemens MS 41.1 ECM pin assignments

IFuel Injection