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Engine Controls - Adjustments - v6 Chevrolet Caprice IV

Adjustments ~459 words

ENGINE MECHANICAL

Before performing any on-vehicle adjustments to fuel or ignition systems, ensure engine mechanical condition is okay.

VALVE CLEARANCE

Note. All models use hydraulic lifters. Adjustments are not required.

IGNITION TIMING

Note. Procedures for timing adjustment are for engines equipped with HEI-EST distributors only. Other engines are equipped with C(3)I, DIS or IDI ignition system. Timing on these systems is not adjustable.

V6 IGNITION TIMING

Note. Some engines are equipped with a socket for a magnetic probe timing meter, located 9.5 degrees ATDC. DO NOT use this location for setting timing using a conventional timing light.

4.3L

  1. Warm engine to normal operating temperature. Disconnect Electronic Spark Timing (EST) by-pass connector, located on wiring harness on right front side of engine, near AIR control valve.
  2. Connect timing light to spark plug No. 1 wire. Loosen distributor hold-down bolt. Set timing to zero degrees BTDC at idle with transmission in Drive. Tighten distributor hold-down bolt, and recheck timing.
  3. Turn engine off. Reconnect EST by-pass connector. Clear ECM code by disconnecting battery negative terminal for at least 30 seconds.

IDLE SPEED & MIXTURE

Note. Idle mixture is controlled by Electronic Control Module (ECM). Adjustment is not possible.

CAUTIONWhen battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in the GENERAL INFORMATION section before disconnecting battery.

IDLE SPEED

Note. Idle mixture is controlled by Electronic Control Module (ECM). Adjustment is not possible.

Note. Incorrect idle speeds are normally caused by dirty throttle plate or vacuum leaks. Ensure all vacuum components are functioning properly.

  1. Idle speed is ECM-controlled. Resetting of IAC valve pintle is the only possible adjustment. To reset IAC valve pintle position, turn ignition on (engine off).
  2. Using a jumper, ground ALDL diagnostic test connector for 5 seconds. Remove jumper from ALDL diagnostic test connector. Turn ignition off for 10 seconds. Start engine, and check for proper idle operation. Refer to underhood emissions label for idle specifications. Clear any trouble codes.

IDLE MIXTURE

Note. Idle mixture is controlled by Electronic Control Module (ECM). Adjustment is not possible.

THROTTLE POSITION (TP) SENSOR

Note. Not all TP sensors are adjustable. For further testing procedures, refer to appropriate TESTS W/CODES or I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.

THROTTLE POSITION SENSOR - 3.8L

Throttle Position (TP) sensor can be adjusted using scan tester or the following procedure.

  1. Ensure engine is at normal operating temperature. Install 3 jumper wires between TP sensor and TP sensor wiring harness connector.
  2. Turn ignition on with engine off. Connect DVOM to Dark Blue and Black wire terminals. With throttle at closed position, adjust TP sensor to obtain specified voltage. See «TP SENSOR ADJUSTMENT VOLTAGE»(/chevrolet/caprice/iv-1990-1996/remont/adjustments/#engine-controls-adjustments-v6) table.
  3. Tighten screws, and recheck readings. Turn ignition off. Remove jumper wires, and reconnect harness connector to TP sensor.
Application(1) Volts
3.1L(2) .29-4.80
3.3L(2) .20-4.00
3.4L(2) .50-4.80
3.8L
VIN L(2) .40-4.00
VIN 1(2) .20-5.00
4.3L(2) .20-5.00
(1) Voltage range is from idle position to wide open throttle position. (2) Not adjustable.
(1)Voltage range is from idle position to wide open throttle position.
(2)Not adjustable.

TP SENSOR ADJUSTMENT VOLTAGE

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