Engine Controls - Adjustments - v8 Chevrolet Caprice IV

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.

IGNITION TIMING - 4.9L

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.

1. Place transmission in Park. Ensure engine is at normal operating temperature. Turn A/C and all accessories off. Ensure system is not in diagnostic mode.
2. Jumper ALDL test terminals "A" and "B". (Scheme 1) Connect timing light to spark plug No. 1 wire. Check ignition timing, and adjust if necessary. See «IGNITION TIMING SPECIFICATIONS»(/chevrolet/caprice/iv-1990-1996/remont/adjustments/#engine-controls-adjustments-v8) table. Tighten distributor, and recheck timing. Remove jumper from ALDL test connector.

IGNITION TIMING - 5.7L (VIN P)

Note. Ignition timing is not adjustable on 5.7L (VIN P).

IGNITION TIMING - 5.0L (VIN E) & 5.7L (VIN 7) EXCEPT CADILLAC

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.

1. Place transmission in Park. Start and warm engine to normal operating temperature. Turn A/C and all accessories off. Ensure CHECK ENGINE light is off.
2. Put Electronic Spark Timing (EST) into by-pass mode by unplugging Set-Timing connector. Connector is a single wire in wiring harness on left side of engine, near AIR control valve. DO NOT unplug 4-wire connector at distributor.
3. Connect timing light to spark plug No. 1 wire. Loosen distributor hold-down bolt. Set timing to specification. See the «IGNITION TIMING SPECIFICATIONS»(/chevrolet/caprice/iv-1990-1996/remont/adjustments/#engine-controls-adjustments-v8) table. Tighten distributor, and recheck timing. Reconnect Set-Timing connector. Clear Electronic Control Module (ECM) trouble code by disconnecting ECM power source or negative battery terminal for at least 30 seconds.

IGNITION TIMING - 5.7L (VIN 7) CADILLAC

1. Place transmission in Park and block drive wheels. Start and warm engine to normal operating temperature. Turn A/C and all accessories off. Ensure SERVICE ENGINE SOON light is off.
2. Ground Ignition Control (IC) by-pass connector. IC by-pass is a single lead wire that breaks out of engine wiring assembly to right of throttle body assembly. see scheme 2 Electronic Control Module (ECM) will set a DTC when IC by-pass connector is grounded.
3. Connect timing light to spark plug No. 1 wire. Loosen distributor hold-down bolt. Place transmission in Drive. Set timing to specification. See the «IGNITION TIMING SPECIFICATIONS»(/chevrolet/caprice/iv-1990-1996/remont/adjustments/#engine-controls-adjustments-v8) table. Tighten distributor, and recheck timing.
4. Turn engine off and disconnect IC by-pass connector from ground. Clear ECM trouble code by disconnecting ECM power source or negative battery terminal for at least 30 seconds.

Scheme 1

IGNITION TIMING SPECIFICATIONS

MINIMUM IDLE - DEVILLE/SIXTY-SPECIAL

1. Warm engine to normal operating temperature. Turn A/C and all accessories off. With ignition on and engine off, select Powertrain Control Module (PCM) override E.5.3., Idle Speed Control (ISC) motor. See appropriate G - TESTS W/ CODES article in this section.
2. Press COOLER button on Electronic Climate Control (ECC) panel to retract ISC motor. Fuel data center should alternately display E.5.3. and 00, indicating override function has started. ISC will slowly move (about 20 seconds) to a fully retracted position.
3. Verify throttle lever rests on minimum idle speed screw. With ISC plunger fully retracted, disconnect ISC harness. If engine stalls at this point, check throttle blades for deposits which might restrict airflow. Clean throttle body as necessary.
4. With ISC fully retracted, plunger should not touch throttle lever. If contact is noted, adjust ISC plunger. Throttle lever must rest on minimum air screw. Ensure throttle cable, TV cable and cruise control cable are not binding. Adjust or replace cables as necessary.
5. Using a tachometer, check minimum idle speed. Use average RPM reading. Adjust minimum idle speed if not as specified, using ISC Adjusting Wrench (J-29607). See «MINIMUM IDLE SPEED - 4.9L»(/chevrolet/caprice/iv-1990-1996/remont/adjustments/#engine-controls-adjustments-v8) table. Ensure no vacuum leaks are present. Check TP sensor adjustment. See «THROTTLE POSITION (TP) SENSOR»(/chevrolet/caprice/iv-1990-1996/remont/adjustments/#engine-controls-adjustments-v8__throttle-position-tp-sensor) . Start engine, and check for proper idle operation.

MINIMUM IDLE (ELDORADO & SEVILLE)

1. Warm engine to normal operating temperature. Turn A/C and all accessories off. Enter diagnostics, and select Powertrain Control Module (PCM) override PS03, Idle Speed Control (ISC) motor. See appropriate G - TESTS W/ CODES article in this section.
2. Press COOLER button on Climate Control Panel (CCP). This action disengages A/C compressor, commands EGR off and turns off alternator. CCP will display 50 to 00. ISC motor will slowly move to a fully retracted position (in about 20 seconds).
3. Ensure throttle lever rests on minimum idle speed screw. Adjust plunger as necessary, using ISC Adjusting Wrench (J-38457). Check throttle lever for binding. Readjust or repair cables causing throttle to bind.
4. Check minimum idle speed displayed on Driver Information Center (DIC). If minimum idle is not as specified, go to step 5) or 6). See «MINIMUM IDLE SPEED - 4.9L»(/chevrolet/caprice/iv-1990-1996/remont/adjustments/#engine-controls-adjustments-v8) table. If minimum idle speed is okay, check TP sensor adjustment. See THROTTLE POSITION (TP) SENSOR.
5. If engine stalls at minimum air (ISC fully retracted), check throttle blades for deposits which might restrict airflow. Clean throttle bores. Clean behind and around throttle plates. Check minimum idle speed displayed on DIC. Use average RPM reading to set minimum idle speed. See «MINIMUM IDLE SPEED - 4.9L»(/chevrolet/caprice/iv-1990-1996/remont/adjustments/#engine-controls-adjustments-v8) table. Check for vacuum leaks.
6. If engine RPM is too high, check for vacuum leaks at throttle body, intake manifold, vacuum fittings, etc. Repair vacuum leaks. Adjust minimum idle screw to obtain specified RPM. See the «MINIMUM IDLE SPEED - 4.9L»(/chevrolet/caprice/iv-1990-1996/remont/adjustments/#engine-controls-adjustments-v8) table. Check TP sensor adjustment. See THROTTLE POSITION (TP) SENSOR. Start engine, and check for proper idle operation.

MINIMUM IDLE SPEED - 4.9L

MAXIMUM ISC EXTENSION - DEVILLE/SIXTY-SPECIAL

1. Before adjusting maximum Idle Speed Control (ISC) extension, check minimum idle and Throttle Position (TP) sensor adjustment. See MINIMUM IDLE under «IDLE SPEED»(/chevrolet/caprice/iv-1990-1996/remont/adjustments/#engine-controls-adjustments-v8) . See «THROTTLE POSITION (TP) SENSOR»(/chevrolet/caprice/iv-1990-1996/remont/adjustments/#engine-controls-adjustments-v8__throttle-position-tp-sensor) .
2. With ignition on and engine off, select ISC MOTOR override E.5.3. See appropriate G - TESTS W/ CODES article in this section. Fully extend ISC motor by pressing WARMER button on Electronic Climate Control (ECC) panel. Fuel data center should alternately display E.5.3 and 99, indicating override function has started.
3. ISC should extend to maximum extend position. With ISC at maximum extended position, TP sensor voltage should be 1.15-1.20 volts. If TP sensor voltage is not 1.15-1.20 volts, adjust ISC plunger clockwise or counterclockwise until TP sensor parameter reads 1.18 volts.
4. Recheck maximum extend setting. Press COOLER button to retract ISC plunger. Wait 5 seconds. Press WARMER button, and check TP sensor voltage. Readjust ISC plunger if necessary.
5. While still in diagnostic mode, turn ignition off. Allow about 20 seconds for ISC to retract and perform a TPS LEARN routine. Re-enter diagnostic mode, and turn ignition off. A successful TPS LEARN will take 2 cycles to occur. Remove alternator disable ground wire. Start engine, and check for proper ISC motor operation.

MAXIMUM ISC EXTENSION - ELDORADO & SEVILLE

1. Before adjusting maximum Idle Speed Control (ISC) extension, check minimum idle and Throttle Position (TP) sensor adjustment. See MINIMUM IDLE under «IDLE SPEED»(/chevrolet/caprice/iv-1990-1996/remont/adjustments/#engine-controls-adjustments-v8) . See «THROTTLE POSITION (TP) SENSOR»(/chevrolet/caprice/iv-1990-1996/remont/adjustments/#engine-controls-adjustments-v8__throttle-position-tp-sensor) .
2. With ignition on and engine off, select ECM ISC MOTOR override ES03. See appropriate G - TESTS W/ CODES article in this section.
3. Fully extend ISC motor by pressing WARMER button on Electronic Climate Control (ECC) panel. Fuel data center display should alternately change from 50 or 00 to 99, indicating override function has started.
4. ISC should extend to maximum extend position. With ISC at maximum extended position, TP sensor parameter should indicate 13.0-13.8 degrees on Driver Information Center (DIC). If TP sensor is not 13.0-13.8 degrees, adjust ISC plunger clockwise or counterclockwise until TP sensor parameter indicates 13.4 degrees on DIC.
5. Recheck maximum extend setting. Press COOLER button to retract ISC plunger. Wait 5 seconds. Press WARMER button, and check TP sensor angle (in degrees). Readjust ISC plunger if necessary.
6. While still in diagnostic mode, turn ignition off. Allow about 20 seconds for ISC to retract and perform a TPS LEARN routine. Re-enter diagnostic mode, and turn ignition off. Successful TPS LEARN takes 2 cycles to occur. Start engine, and check for proper ISC motor operation. Clear codes.

EBTCM RELEARN PROCEDURE - 5.7L (VIN 7) FLEETWOOD

Note. On 5.7L (VIN 7) "D" Body, whenever a NEW throttle body assembly or TP sensor is installed, the Electronic Brake & Traction Control Module (EBTCM) should go through a relearn procedure to ensure effective engine torque reduction during traction control events.

1. Turn ignition off. Using Tech 1 scan tester, install scan tester to vehicle's diagnostic connector. Use Tech 1 scan tester with "Mass Storage/Chassis Cartridge". Turn ignition on.
2. Follow scan tester's menu to reach ABS/TCS features. Select F5 (TPS LEARN). Press UP arrow to begin relearn procedure. Wait for Tech 1 scan tester to indicate COMPLETE. Turn ignition off. Disconnect scan tester.

IAC VALVE RESET (5.0L VIN E & 5.7L VIN P & 7 EXCEPT "D" BODY)

Note. On 5.0L (VIN E) and 5.7L (VIN P & 7), idle speed is controlled by ECM and will normally vary. Adjustment is not required. Refer to following IAC VALVE RESET procedure.

1. Idle speed is ECM controlled. Resetting of IAC valve pintle is only possible adjustment. To reset IAC valve pintle position, depress accelerator pedal slightly. Start engine, and release accelerator pedal. Run engine for 5 seconds.
2. Turn engine off for 10 seconds. Restart engine, and check for proper idle operation. Clear any trouble codes.

IDLE MIXTURE

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

THROTTLE POSITION (TP) SENSOR

Note. All testing procedures are made with engine at normal operating temperature. Not all TP sensors are adjustable. For further testing procedures, see appropriate G - TESTS W/ CODES or I - SYS/COMP TESTS article in this section.

THROTTLE POSITION SENSOR - 4.9L

1. Turn ignition off. Disable alternator by grounding Green harness connector plug adjacent to alternator. Turn ignition on, engine off. Enter diagnostic mode, and select PCM override PS03 (ISC motor). See appropriate G - TESTS W/ CODES article in this section.
2. Press COOLER button to retract ISC motor to minimum air setting. Loosen TP sensor screws enough to permit sensor rotation. Open throttle slightly, and allow throttle lever to snap shut against minimum air screw.
3. Adjust TP sensor so parameter display is zero degrees. Tighten TP sensor mounting screws. Recheck parameter and ensure TP sensor parameter is within .5 degrees of reading.

THROTTLE POSITION TP SENSOR ADJUSTMENT VOLTAGE

See also:
• IGNITION TIMING SPECIFICATIONS
• THROTTLE POSITION (TP) SENSOR