Engine Controls - Adjustments Lexus LS I

ENGINE COMPRESSION

Warm engine to normal operating temperature. Disconnect cold start injector. Disconnect crank angle sensors. Remove spark plugs. Ensure battery is fully charged. Check engine compression with throttle fully open and engine cranking at specified cranking RPM.

ENGINE COMPRESSION TEST

Scheme 1

Scheme 2

Scheme 3

1. With engine cold, disconnect negative battery cable. Remove air duct and dust covers. Remove 2 bolts, nut and throttle body cover. Remove air hose from AIC valve. Remove hose from power steering air control valve. Remove 2 bolts, disconnect air connector pipe from throttle body and remove air connector pipe.
2. Remove 2 bolts and disconnect front claw groove of upper cover from claw of lower cover. Remove upper high tension wire cover. Disconnect PCV hose from PCV valve on left cylinder head. Remove 3 bolts and wire cover. Remove 4 bolts, right timing belt cover and 3 gaskets.
3. Disconnect vacuum hose from EVAP BVSV. Remove 4 bolts and disconnect wire grommet from left timing belt cover. Remove timing belt cover and 3 gaskets. Disconnect spark plug wires from spark plugs. Remove spark plugs. Remove bolt and spark plug wire clamp. Remove 4 clamps.
4. Disconnect throttle body sensor connectors. Disconnect water by-pass pipe (rear water by-pass joint) from clamp on engine wire cover. Disconnect water by-pass pipe from hose. Remove 2 bolts and 2 nuts, disconnect PCV hose from cylinder head cover and remove throttle body with gasket.
5. Disconnect engine wire from wire bracket on right cylinder head. Remove bolt and pull out dipstick guide with dipstick. Remove both cylinder head covers.
6. Turn crankshaft pulley and align its groove with "0" timing mark on No. 1 timing belt cover. Ensure that timing marks of the camshaft pulleys and timing belt rear plates are aligned. If not, rotate crankshaft one revolution (360 degrees) and align marks again.
7. Measure and record clearance of intake valves on cylinders No. 1, 2, 5, 7 and 8, and exhaust valves on cylinders No. 1, 4 and 8. (Scheme 1)& 2. Rotate crankshaft pulley 360 degrees (1 revolution) and align timing marks. Measure and record clearance of intake valves on cylinders No. 3, 4 and 6, and exhaust valves on cylinders No. 2, 3, 5, 6, and 7. (Scheme 1)& 2.
8. Determine if clearance is within specification. See LS400 VALVE CLEARANCE SPECIFICATIONS TABLE in this article. If clearance adjustment is required, rotate crankshaft pulley to position lobe upward on the valve to be adjusted.
9. Use Valve Clearance Adjuster (SST 09248-55011) to press valve lifter downward. Press valve lifter downward using SST (A) and install SST (B) between camshaft and valve lifter and remove SST (A). (Scheme 3) Using compressed air and magnet, remove adjusting shim by blowing air into shim hole.
10. Using a micrometer, measure thickness of shim just removed. Select a new shim that will give correct valve clearance. See LS400 VALVE CLEARANCE SPECIFICATIONS TABLE in this article. Shims are available in thickness of.0984-.1299" (2.50-3.30 mm) in.002" (.05 mm) increments.
11. Install proper shim. Using SST (A), press downward on valve lifter and remove SST (B). Recheck valve clearance. Reinstall cylinder head covers using new gaskets. Tighten cylinder head cover bolts to 52 INCH lbs. (5.9 N.m). Install remaining components. Fill cooling system and check for leaks.

VALVE CLEARANCE SPECIFICATIONS

IGNITION TIMING

Scheme 4

Scheme 5

1. Ensure engine is at normal operating temperature. Connect timing light to No. 6 spark plug wire. Connect tachometer to "IG-" terminal of engine check connector. Set tachometer to 4-cylinder range. (Scheme 4)
2. Install jumper wire between terminals "TE1" and "E1"of engine check connector. (Scheme 5) Ensure idle speed is within specification. See IDLE SPEED SPECIFICATIONS TABLE in this article. Note that base timing is within specification. See IGNITION TIMING (Degrees BTDC @ RPM) table in this article. Remove jumper wire from engine check connector.
3. If ignition timing is not within specifications, check the following: Ensure throttle valve is fully closed. Ensure there is continuity between terminals "IDL" and "E2" of throttle position sensor. Check valve timing.

IGNITION TIMING

IDLE SPEED & MIXTURE

Note. Mixture adjustment IS NOT a part of normal tune-up procedure and should only be performed when mixture control unit is replaced or vehicle fails emissions testing.

IDLE SPEED

Note. Idle speed is controlled by the computer and idle speed control system.

1. Install tachometer to proper terminals. (Scheme 4) Start engine and note if idle speed is within specification. See IDLE SPEED SPECIFICATIONS TABLE in this article.
2. If idle speed is not within specification, check the ISC valve, wiring and ECU. See IDLE SPEED CONTROL (ISC) SYSTEM in SYSTEM/COMP TESTS article.

IDLE SPEED SPECIFICATIONS

IDLE MIXTURE

Note. Idle mixture must be checked with air cleaner installed, all air intake system hoses and vacuum lines connected, EFI system wiring connectors tight, transmission/transaxle in Neutral, all accessories and cooling fan off (if equipped) and engine at normal operating temperature.

Scheme 6

Scheme 7

1. Ensure idle speed is within specification. Install jumper wire between "VF1" or "VF2" and "E1" terminals of check engine connector. Connect positive (+) probe of voltmeter to terminal "VF1" for left bank or "VF1" for right bank and negative (-) probe to terminal "E1". (Scheme 6)& 7.
2. Start engine and maintain engine RPM at 2500 RPM for approximately 2 seconds. With engine RPM at 2500, count the amount of times that voltmeter fluctuates between the specified voltage. See IDLE MIXTURE TEST SPECIFICATIONS TABLE in this article.
3. If the amount of fluctuations is less than the minimum amount, check for air leaks at the air induction system, defective airflow meter or throttle body.
4. If fluctuations were within specification, accelerate and hold engine at 2500 RPM for approximately 2 minutes. Install exhaust gas analyzer probe in tailpipe at least 1.3 feet. Wait one minute and check idle mixture readings. If readings are not within specification, see IDLE MIXTURE TROUBLE SHOOTING TABLE in this article.

IDLE MIXTURE TEST SPECIFICATIONS

IDLE MIXTURE TROUBLE SHOOTING

Scheme 8

1. Loosen TPS mounting screws. Unplug TPS and connect ohmmeter between throttle position sensor "IDL" and "E2" terminals. (Scheme 8) Insert a.020" (.50 mm) on ES250 or.0157" (.40 mm) on LS400 feeler gauge between throttle stop screw and lever.
2. Rotate TPS clockwise until ohmmeter deflects. Tighten mounting screws. Using specified feeler gauge, recheck adjustment. See THROTTLE POSITION SENSOR ADJUSTMENT TABLE. Remove ohmmeter and connect TPS.

THROTTLE POSITION SENSOR ADJUSTMENT

DASHPOT CONTROL SYSTEM

For testing and adjustment procedures, see DASHPOT CONTROL SYSTEM in SYSTEM/COMP TESTS article in the ENGINE PERFORMANCE Section.