Engine Controls - Adjustments: Other Lexus SC I

ENGINE MECHANICAL

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

VALVE CLEARANCE

Note. Check and adjust valves with engine cold.

Scheme 3

Note. Check and adjust valves with engine cold.

1. Remove engine splash shield from underneath vehicle. Drain engine coolant. Disconnect control cables from throttle linkage. Remove intake air hose. Remove EGR pipe and gasket. Disconnect EGR temperature sensor connector. Remove throttle body bracket between throttle body and cylinder head.
2. Remove throttle body and intake air connector (pipe between throttle body and air intake chamber) as an assembly. Disconnect spark plug wires from plugs and wire holders. Remove timing belt cover No. 3 (upper cover). Remove cylinder head covers No. 1 (left side), No. 2 (center) and No. 3 (right side).
3. Rotate crankshaft clockwise until piston No. 1 is at TDC of compression stroke. Ensure groove on crankshaft pulley aligns with "0" timing mark on timing belt cover. Timing marks on camshaft pulleys should align with timing marks on timing belt cover No. 4 (upper inner cover).
4. Measure and record clearance of intake valves for cylinders No. 1, 2 and 4, and exhaust valves for cylinders No. 1, 3 and 5. (Scheme 4) Rotate crankshaft 360 degrees. Measure and record clearance of intake valves for cylinders No. 3, 5 and 6, and exhaust valves for cylinders No. 2, 4 and 6.
5. Compare measured clearance with specified clearance. See «VALVE CLEARANCE SPECIFICATIONS»(ref-22008-S41703706702001010300000) table. If clearance is within specification, go to step 9). If clearance is not within specification, rotate crankshaft until camshaft lobe of valve to be adjusted is facing upward, away from shim. VALVE CLEARANCE SPECIFICATIONS Application In. (mm) Intake.006-.010 (.15-.25) Exhaust.010-.014 (.25-.36)
6. Using a screwdriver, rotate valve lifter until notch is at a 90-degree angle to camshaft (perpendicular), facing centerline of cylinder head. Using Valve Lifter Press (SST 09248-05410), press valve lifter downward. (Scheme 3)
7. Position Valve Lifter Stopper (SST 09248-05420) between camshaft and valve lifter to keep valve lifter held down. Remove valve lifter press. Using a small screwdriver and magnet, remove shim. Select a shim of appropriate thickness. See «SELECTING SHIMS»(ref-22008-S15395903432001010300000) at end of VALVE CLEARANCE.
8. Place shim onto valve lifter with imprinted numbers facing down. Press downward on valve lifter using valve lifter press, and remove valve lifter stopper. Recheck valve clearance to ensure it is correct.
9. To complete installation, reverse removal procedure. Remove old cylinder head cover seal packing material. Install NEW Seal Packing (08826-00080) material. (Scheme 5) Use NEW gaskets as necessary. Tighten nuts and bolts to specification. See «TORQUE SPECIFICATIONS»(ref-22008-S27430401462001010300000).

Scheme 4

Scheme 5

SELECTING SHIMS

Shims are available in thicknesses of .0984-.1299" (2.50-3.30 mm), in increments of .002" (.05 mm). Using a micrometer, measure thickness of used shim (shim that was removed). Use the following formulas to determine how thick the new shim should be

1. Intake Valve Subtract .008" (.20 mm) from the measured (actual) valve clearance. Add the result to the thickness of the used shim. The final result represents the thickness of the new shim.
2. Exhaust Valve Subtract .012" (.30 mm) from the measured (actual) valve clearance. Add the result to the thickness of the used shim. The final result represents the thickness of the new shim.

IGNITION TIMING

Note. Ignition timing is not adjustable.

1. Warm engine to normal operating temperature. Turn ignition off. Connect timing light to spark plug wire for cylinder No. 1.
2. Remove instrument panel fuse box cover and connect scan tester to Data Link Connector (DLC) No. 3. (Scheme 6) Scan tester is used to read engine RPM.
3. Apply parking brake. Ensure all accessories are off. Place transmission Neutral. Start engine and maintain engine speed at 2500 RPM for 90 seconds and then allow engine to idle. Ensure idle speed is 650-750 RPM.
4. Install Jumper Wire (SST 09843-18020) between terminals TE1 and E1 of DLC No. 1. (Scheme 6) Connector is located near air intake chamber. Check base timing. See «IGNITION TIMING»(ref-22008-S21011428632001010300000) table.
5. If base timing is correct, go to next step. If base timing is incorrect, loosen distributor hold-down bolt. Adjust base timing by rotating distributor. Tighten distributor hold-down bolt. Go to next step.
6. Remove jumper wire from DLC No. 1. Ensure advance timing is within specification. See «IGNITION TIMING»(ref-22008-S21011428632001010300000) table. Remove timing light and scan tester.

IGNITION TIMING (Degrees BTDC @ RPM)

Scheme 6

IDLE SPEED

Note. Idle speed is controlled by the ECM and is not adjustable. Check and adjust idle speed with air cleaner installed, all air intake system hoses and vacuum lines connected, electronic fuel injection system wiring connectors tight, transmission/transaxle in Neutral, ignition timing properly set, A/C and all accessories off and engine at normal operating temperature.

1. Remove fuse box cover and connect scan tester to Data Link Connector (DLC) No. 3. (Scheme 6) Scan tester is used to read engine RPM.
2. Apply parking brake. Place transaxle in Neutral. Start engine and maintain engine at 2500 RPM for 90 seconds and then allow engine to idle. Ensure idle speed is 650-750 RPM.
3. If idle speed is not 650-750 RPM, check Idle Air Control (IAC) valve, wiring and Electronic Control Module (ECM). See IDLE CONTROL SYSTEM in SYSTEM & COMPONENT TESTING article. Remove scan tester.

IDLE MIXTURE

Note. Idle mixture is controlled by the ECM and is not adjustable. If vehicle fails emissions test, Heated Oxygen Sensor (HO2S) may be faulty, causing a trouble code to set. See SELF-DIAGNOSTICS article.

THROTTLE POSITION (TP) SENSOR

Note. Vehicles with Traction Control System (TRAC) are equipped with a main TP sensor and a sub-TP sensor. Use the following procedure to adjust main TP sensor. To adjust sub-TP sensor, see SUB-THROTTLE POSITION (SUB-TP) SENSOR .

SUB-THROTTLE POSITION (SUB-TP) SENSOR

Note. Vehicles with Traction Control System (TRAC) are equipped with a main TP sensor and a sub-TP sensor. Use the following procedure to adjust sub-TP sensor. To adjust main TP sensor, see THROTTLE POSITION (TP) SENSOR .

DASHPOT

Warm engine. Ensure idle speed is 650-750 RPM. While fully extending dashpot rod with a screwdriver, check engine speed. If engine speed (dashpot set speed) is not within specification, rotate dashpot adjusting screw as necessary. See DASHPOT SET SPEED SPECIFICATIONS table.

DASHPOT SET SPEED SPECIFICATIONS

THROTTLE OPENER

Warm engine to normal operating temperature. Ensure idle speed is 650-750 RPM. Disconnect vacuum hose from throttle opener, and plug hose end. Run engine at 2500 RPM then release throttle. See THROTTLE OPENER SET SPEED SPECIFICATIONS table. If throttle opener set speed is not as specified

1. Replace throttle body.

THROTTLE OPENER SET SPEED SPECIFICATIONS

PARK/NEUTRAL POSITION (PNP) SWITCH

Loosen bolt that secures PNP switch to transmission. Move shift shaft into Neutral (2 detents from Park). Align groove on shift shaft with neutral basic line on PNP switch. (Scheme 7)or 14. Tighten bolt.

Scheme 7