Lexus ES300 (2002 year). Manual — part 139

ENGINE – 1MZ-FE ENGINE

EG-10

211EG06

Intake Valves

Exhaust Camshaft

VVT-i Controller

Intake Camshafts

VVT-i Controller

Exhaust Camshaft

Exhaust
Valves

VALVE MECHANISM

1. General

The valves are directly opened and closed by 4 camshafts.
The exhaust camshafts are driven by a timing belt, while the intake camshafts are driven through gears

on the exhaust camshafts.

The VVT-i system used for the intake camshaft is adopted to realize excellent fuel economy, engine perfor-

mance and reduce exhaust emissions.
For details, see page EG-41 in the VVT-i system section.

ENGINE – 1MZ-FE ENGINE

EG-11

187EG15

No.2 Camshaft
(Exhaust)

Scissors Gear Mechanism

VVT-i Controller

Timing Rotor

Scissors Gear Mechanism

Driven Gear

No.4 Camshaft
(Exhaust)

No.3 Camshaft
(Intake)

No.1 Camshaft
(Intake)

2. Camshafts

The camshafts are made of cast iron alloy.
In conjunction with the adoption of the VVT-i system, an oil passage is provided in the intake camshaft

in order to supply engine oil t to the VVT-i system.

A VVT-i controller has been installed on the back of the intake camshaft to vary the timing of the intake

valves.

To detect the camshaft position, a timing rotor that is provided on the VVT-i controller is used to generate

3 pulses for every 2 revolutions of the crankshaft.

The intake camshafts are driven by gears on the exhaust camshafts. The scissors gear mechanism is used

on drive gear of the exhaust camshaft to control backlash and suppress gear noise.

ENGINE – 1MZ-FE ENGINE

EG-12

208EG64

Camshaft

Adjusting Shim

Valve Lifter

Valve

Adjusting Shim

Cutout

Valve Llifter

187EG17

Service Tip

The adjusting shims are available in 17 sizes in increments of 0.050 mm (0.0020 in.), from 2.500 (0.0984
in.) to 3.300 (0.1299 in.).
For details, refer to see the 2002 LEXUS ES300 Repair Manual (Pub. No. RM911U).

3. Intake and Exhaust Valve and Valve Lifter

Narrower valve stems have been adopted to reduce the intake and exhaust resistance and for weight reduc-

tion.

The adjusting shim has been located directly above the valve lifter. This construction allows the adjusting

shim to be replaced without removing the camshaft, which improves the serviceability during valve clear-
ance adjustment.

A cutout is provided in the valve lifter to improve the serviceability of replacing the adjusting shims.

ENGINE – 1MZ-FE ENGINE

EG-13

198EG40

No.1 Idler
(Tension Adjuster)

Timing Belt
Tensioner

Camshaft Timing Pulleys

No.2 Idler

Water
Pump
Pulley

Crankshaft Timing
Pulley

198EG41

Plunger
Spring

Return
Spring

Belt Tensioner

4. Timing Belt

The timing belt tooth configuration has been de-
signed to help to reduce noise and to enable the
belt to transmit power under high load factors.

5. Timing Belt Tensioner

The timing belt tensioner uses a spring and silicon
oil damper, and maintains proper timing belt ten-
sion at all times.
The timing belt tensioner suppresses noise gener-
ated by the timing belt.