Test the map and tps. If the throttle is controlled electronically, also test the accelerator position sensor. Make sure the tps signal changes smoothly as the throttle is opened.
Manifold Absolute Pressure (MAP) Sensor
OPERATION The Manifold Absolute Pressure (MAP) sensor is a device which monitors manifold vacuum. It is either mounted on the firewall or throttle body and is linked electrically to the on-board computer. The MAP transmits information on manifold vacuum conditions to the computer. This data determines engine load and is used with data from other sensors to adjust the air/fuel mixture.
On the 2.5L engine, the MAP sensor is mounted in the right rear side of the engine compartment. It is connected to the throttle body by vacuum line. The MAP sensor on V6 and V8 engines is mounted to the throttle body. It is connected by an L-shaped rubber fitting. The V10 MAP sensor is found on the right side of the intake manifold and senses vacuum in the manifold.
TESTING See Figure 1
To completely test this sensor and its circuitry, you will need a DRBII scan tool, or equivalent. This is a test of the MAP sensor only. This test is for all engines except the 4-cylinder.
On the V6 and V8 engines: inspect the rubber fitting from the MAP sensor to the throttle body. Repair if necessary.On the V6 and V8 engines: test the MAP sensor output voltage at the connector between terminals A and B (see drawing). With the ignition ONand the engine OFF , the output voltage should be 4-5 volts.Test the engine controller terminal No. 1 for the same voltage to confirm that the wiring is in good shape. Repair if necessary.Test the MAP sensor voltage at the sensor connector between terminals A and C with the ignition ON . The voltage should be 4.5-5.5 volts. Also check terminal No. 6 of the engine controller wiring harness for the same voltage. Repair or replace the wiring as necessary.Test the engine controller pin-1 for the same voltage to verify the wire harness condition.
Fig. 1: Terminal connections for testing the MAP sensor
Throttle Position Sensor (TPS)
The Throttle Position Sensor (TPS) is located on the throttle body and tells the computer when the engine is at idle, off-idle, or at Wide-Open Throttle (WOT). At idle, the computer cancels the spark advance. Idle speed is computer-controlled through the automatic idle speed motor.
TESTING To completely test this sensor and circuitry, you need the DRBII scan tool, or equivalent. This is a test of the sensor only. This test applies only to V6, V8 and V10 engines.
This test requires a digital voltmeter. The sensor must be checked on the vehicle with its 3-wire connector engaged to the sensor. The center terminal wire of the sensor connector is the output terminal.
Remove the air cleaner housing.Attach the positive lead of the voltmeter to the center terminal of the sensor harness.Attach the negative lead of the voltmeter to a good ground.With the ignition key in the ON position and engine not running, check the sensor output voltage at the center terminal wire of the connector. Check this at idle (throttle plate closed) and at Wide Open Throttle (WOT). At idle, the sensor output voltage should be greater than 200 millivolts. At WOT, the sensor output voltage should be less than 4.8 volts. The output voltage should increase gradually as the throttle plate is slowly opened from idle to WOT.If the sensor does not meet specifications, replace it.
Fig. 1: Common TPS mounting-V6 and V8 engines
Fig. Fig. 2: Common TPS mounting-V10 engine