Scoupe L4-1468cc 1.5L SOHC VIN J MFI (1994)
Mass Air Flow Sensor: All Technical Service Bulletins
T/P & MAF Sensor - Poor Idle/Poor Driveability
Group: ENGINE ELECTRICAL
Number: 96-36-003
Date: MAY 1996
Model: 93-95 SCOUPE, 96 ELANTRA, 95-96 ACCENT
Subject
THROTTLE POSITION AND MASS AIR FLOW
SENSOR TROUBLESHOOTING
SERVICE INFORMATION:
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The Throttle Position Sensor (TPS) signal indicates the angle of the throttle plate. The output voltage of the TPS is directly proportional to the angle
of the throttle plate.
^
The Mass Air Flow (MAF) sensor measures the mass flow rate of the air entering the engine. The output voltage of the MAF sensor is directly
proportional to the mass flow rate of the air entering the engine.
The output voltages from these sensors are used by the Engine Control Module (ECM) in conjunction with other sensor signals to calculate engine load.
These signals are critical in determining fuel injection pulse width and ignition timing.
CONDITION:
The customer may experience one or more of the following conditions:
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Poor idle quality
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Cyclic fluctuating idle
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Poor driveability (surging, hesitation, etc.)
DIAGNOSIS:
When diagnosing the driveability conditions listed above, the stability of the TPS and MAF signals should be verified. At idle and steady cruise, the TPS
and MAF signals should be steady voltages. If a fluctuating signal is observed, the connection at the related sensor should be verified. Plots using HDS
are shown to illustrate normal TPS and MAF signals at idle. A third plot illustrates an erratic TPS signal at idle taken from a vehicle with a poor contact
at the sensor connection. See following plot illustrations.
SERVICE PROCEDURE:
1.
Turn the ignition key to the OFF position and remove the key.
2.
Disconnect the sensor believed to contribute to the condition. Refer to the appropriate shop manual for the location and connector removal
procedure.
3.
Inspect the connector socket and pins for contamination and proper alignment.
4.
Clean the connector ends with electrical contact cleaner.
5.
Reconnect the connector.
6.
Start the engine and verify the signal stability using a voltmeter or HDS.
