Engine Controls - Adjustments: Other Lexus GS I

ENGINE MECHANICAL

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

VALVE CLEARANCE

Note. Adjust valves with engine cold.

GS300

1. Disconnect negative battery cable. Wait at least 90 seconds to allow air bag system back-up power supply to be depleted. Drain engine coolant. Disconnect control cables from throttle linkage. Remove intake air hose. Remove EGR pipe and gasket. 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. Remove timing belt cover No. 3 (upper outer cover). Remove cylinder head rear cover (small cover on top of cylinder head, near rear end).
3. Disconnect spark plug wires from plugs and wire holders. Remove cylinder head covers and gaskets. Rotate crankshaft clockwise until cylinder No. 1 is at TDC of compression stroke. Groove on crankshaft pulley should be aligned with "0" timing mark on timing belt cover, and timing marks on camshaft pulleys should be aligned 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 3) 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-21740-S18303900112001010300000) 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.
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 at end of «VALVE CLEARANCE»(ref-21740-S16898184942001010300000).
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. Use NEW gaskets as necessary. Tighten nuts and bolts to specification. See «TORQUE SPECIFICATIONS»(ref-21740-S27268978092001010300000).

Scheme 3

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

DATA LINK CONNECTOR (DLC) NO. 1

Note. Data Link Connector (DLC) No. 1 is located

1. On front end of air intake chamber.

1. Ensure engine is at normal operating temperature. Connect timing light magnetic pick-up to spark plug wire for cylinder No. 1. Connect tachometer test lead to terminal IG- of DLC No. 1, located on front end of air intake chamber. (Scheme 4) Connect jumper wire between terminals TE1 and E1 of DLC No. 1.
2. Ensure idle speed is within specification. See «IDLE SPEED SPECIFICATIONS»(ref-21740-S28627676812001010300000) table under IDLE SPEED & MIXTURE. Check base timing. See «IGNITION TIMING»(ref-21740-S01670412562001010300000) table. If base timing is within specification, go to next step. If base timing is not within specification, adjust timing by rotating distributor, then go to next step.
3. Disconnect jumper wire from DLC No. 1. Check controlled timing. See «IGNITION TIMING»(ref-21740-S01670412562001010300000) table. Ensure controlled timing is within specification. If controlled timing is not within specification, problem exists in engine control system.

IGNITION TIMING (Degrees BTDC @ RPM)

Scheme 4

IDLE SPEED

Note. Idle speed is controlled by the ECM and is not adjustable.

Connect tachometer to terminal IG- of DLC No. 1. (Scheme 4) See DATA LINK CONNECTOR (DLC) NO. 1 under IGNITION TIMING. Start engine. If idle speed is not within specification, go to IDLE CONTROL SYSTEM in SYSTEM & COMPONENT TESTING article. See IDLE SPEED SPECIFICATIONS table.

IDLE MIXTURE

Note. Idle mixture is controlled by the ECM and is not adjustable. If vehicle fails emissions test, oxygen sensor (O2S) 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.

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 screw on dashpot 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 bolts that secure 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 5) Tighten bolt(s).

Scheme 5