Lexus RX300 (MCU15). Manual — part 429

EM0AY–04

A04692

CO/HC Meter

–

ENGINE MECHANICAL

CO/HC

EM–1

LEXUS RX300 (RM785E)

CO/HC

INSPECTION

HINT:
This check is used only to determine whether or not the idle CO/
HC complies with regulations.
1.

INITIAL CONDITIONS

(a)

Engine at normal operating temperature

(b)

Air cleaner installed

(c)

All pipes and hoses of air induction system connected

(d)

All accessories switched OFF

(e)

All vacuum lines properly connected

(f)

EFI system wiring connectors fully plugged

(g)

Ignition timing check correctly

(h)

Transmission in neutral position

(i)

Tachometer and CO/HC meter calibrated by hand

2.

START ENGINE

3.

RACE ENGINE AT 2,500 RPM FOR APPROX. 180
SECONDS

4.

INSERT CO/HC METER TESTING PROBE AT LEAST
40 cm (1.3 ft) INTO TAILPIPE DURING IDLING

5.

IMMEDIATELY CHECK CO/HC CONCENTRATION
AT IDLE AND/OR 2,500 RPM

HINT:
When doing the 2 mode (idle and 2,500 rpm) test, these mea-
surement order prescribed by the applicable local regulations.

EM–2

–

ENGINE MECHANICAL

CO/HC

LEXUS RX300 (RM785E)

6.

TROUBLESHOOTING

If the CO/HC concentration does not comply with regulations,
troubleshoot in the order given below.
See the table below for possible causes, and then inspect and
correct the applicable causes if necessary.

CO

HC

Problems

Causes

Normal

High

Rough idle

3. Faulty ignitions:

S Incorrect timing

S Fouled, shorted or improperly gapped plugs

4. Incorrect valve clearance

5. Leaky intake and exhaust valves

6. Leaky cylinders

Low

High

Rough idle

(Fluctuating HC reading)

1. Vacuum leaks:

S PCV hoses

S Intake manifold

S Air intake chamber

S Throttle body

S ISC valve

S Break booster line

2. Lean mixture causing misfire

High

High

Rough idle

(Black smoke from exhaust)

1. Restricted air filter

2. Plugged PCV valve

3. Faulty EFI systems:

S Faulty pressure regulator

S Defective water temperature sensor

S Faulty engine ECU

S Faulty injectors

S Faulty throttle position sensor

S Faulty air flow meter

P19471

Compression Gauge

EM0AZ–02

–

ENGINE MECHANICAL

COMPRESSION

EM–3

LEXUS RX300 (RM785E)

COMPRESSION

INSPECTION

HINT:
If there is lack of power, excessive oil consumption or poor fuel
economy, measure the compression pressure.
1.

REMOVE OUTER COWL TOP PANEL
(See page EM–75)

2.

WARM UP AND STOP ENGINE

Allow the engine to warm up to normal operating temperature.
3.

REMOVE IGNITION COILS (See page IG–6)

4.

REMOVE SPARK PLUGS

Using a 16 mm plug wrench, remove the 6 spark plugs.
5.

CHECK CYLINDER COMPRESSION PRESSURE

(a)

Insert a compression gauge into the spark plug hole.

(b)

Fully open the throttle.

(c)

While cranking the engine, measure the compression
pressure.

HINT:
Always use a fully charged battery to obtain engine speed of
250 rpm or more.
(d)

Repeat steps (a) through (c) for each cylinder.

NOTICE:
This measurement must be done in as short a time as pos-
sible.

Compression pressure:
1,500 kPa (15.3 kgf/cm

2

, 218 psi)

Minimum pressure:
1,000 kPa (10.2 kgf/cm

2

, 145 psi)

Difference between each cylinder:
100 kPa (1.0 kgf/cm

2

, 15 psi) or less

(e)

If the cylinder compression in 1 or more cylinders is low,
pour a small amount of engine oil into the cylinder through
the spark plug hole and repeat steps (a) through (c) for
cylinders with low compression.

S

If adding oil helps the compression, it is likely that
the piston rings and/or cylinder bore are worn or
damaged.

S

If pressure stays low, a valve may be sticking or
seating is improper, or there may be leakage past
the gasket.

6.

REINSTALL SPARK PLUGS

7.

REINSTALL IGNITION COILS (See page IG–7)

8.

REINSTALL OUTER COWL TOP PANEL
(See page EM–82)