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idling properly, exhaust gases are not entering the com
bustion chamber. The probable cause is a plugged pas
sage between the EGR valve and the intake manifold.
If the engine idles improperly and the rpm is not
noticeably affected by compressing the EGR diaphragm,
the EGR valve is not preventing the flow of exhaust gas
during idle. There is either a defect in the vacuum hoses,
hose routings or the valve itself.
EGR Valve Replacement
Removal
(1) For four- and eight-cylinder engines, remove air
cleaner assembly.
(2) Disconnect vacuum hoses.
(3) Remove two retaining screws/nuts from
manifold.
(4) Remove EGR valve and gasket.
(5) Clean EGR pintle, if necessary. Refer to EGR
Valve Maintenance.
(6) Discard gasket and clean all gasket mating
surfaces.
Installation
(1) Install gasket and EGR valve.
(2) Install retaining screws/nuts and tighten.
(3) Connect vacuum hoses and install air cleaner
assembly, if removed.
NOTE: For correct vacuum hose routings, refer to fig
ures U-139, U-UO and U-Ul.
EGR Valve Maintenance
Remove all carbon deposits from the stainless steel
metering pintle of the valve with a wire brush. After
cleaning, depress the diaphragm, cap the vacuum inlet
and repeatedly open the EGR valve manually by press
ing down on the diaphragm and releasing. Pintle should
remain retracted. If it does not, diaphragm has a leak
and valve must be replaced.
On six-cylinder engines, carbon deposits will collect
more rapidly in the exhaust gas discharge passage (up
per hole). If the deposits cannot be removed with a
spiral-type wire brush, a 9/16-inch (14 mm) drill bit may
be used. Coat the tip of the drill bit with heavy grease
and use locking pliers to rotate it in the discharge
passage.
EGR CTO VALVE
The EGR CTO valve is located in the coolant passage
at the right rear of the cylinder head for four-cylinder
engines, on the intake manifold for six-cylinder engines
and either on the intake manifold adjacent to the oil
filler tube or at the right rear corner of the engine
adjacent to the EGR valve for eight-cylinder engines.
FUEL SYSTEMS
1J-75
The inner port(s) connects by hose to the EGR port at
the carburetor (ported vacuum), the outer port (E) con
nects to the EGR valve (or to the TVS for four-cylinder
engines, fig. 1J-139).
When the coolant temperature is below the calibrated
switching temperature of the CTO valve there is no
vacuum applied to the EGR valve. The EGR CTO valve
opens at 100°F (38°C) for four-cylinder engines and at
115°F (46°C) for six- and eight-cylinder engines, and can
be identified by its black body or a black paint dab.
EGR CTO Valve Functional Test
NOTE: Engine coolant temperature must be 10°F
(5.6°C) below the calibrated opening temperature.
(1) Inspect vacuum hoses for air leaks and correct
routings (figs. U-139,140 and 141).
(2) Disconnect vacuum hose at EGR valve. Connect
hose to vacuum gauge.
WARNING: Use extreme caution when engine is oper
ating. Do not stand in direct line with fan. Do not put
hands near pulleys, belts or fan. Do not wear hose
clothing.
(3) Operate engine at 1500 rpm. No vacuum should
be indicated on gauge. If vacuum is indicated, replace
EGR CTO valve.
(4) Idle engine until coolant temperature exceeds
100°F (38PC) for four-cylinder engines and 115°F (46°C)
for six- and eight-cylinder engines.
NOTE: The coolant temperature gauge pointer will be
approximately midway between the cold mark and the
beginning of the normal operating temperature band
when the engine coolant temperature is 115°F U6°C).
(5) Accelerate engine to 1500 rpm. Carburetor por
ted vacuum should be indicated on vacuum gauge. If not,
replace EGR CTO valve.
EGR CTO Valve Replacement
Removal—Four-Cylinder Engine
WARNING: Serious burns can result ifpressure is not
released and if hot coolant is not drained before remov
ing valve.
(1) Drain coolant from radiator.
(2) Disconnect vacuum hoses.
(3) Use open-end wrench to remove valve from right
rear side of cylinder head.
Installation—Four-Cylinder Engine
(1) Install EGR CTO valve on cylinder head.
-
(2) Connect vacuum hoses.
(3) Install coolant and purge air from cooling
system.
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Troubleshooting
