1990 Lexus LS 400FACTORY OEM SERVICE PROCEDURE

Valve Clearance

  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. See Fig 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. See Fig 1 & 2.
    Fig 1: Adjusting LS400 Valves in Proper Sequence (Step 1)
    G90G20764Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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