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12
ROUGH ENGINE IDLE (continued)
Throttle Valve
Switch
1. Take the cover off of the throttle
valve switch and verify that the
contacts are open with the throttle at
idle position. If throttle is placed in
wide open position, then the contacts
should make and the following reading
should be detected.
a. Pins 18 and 3 - 0 ohms with
throttle valve wide open
Idle Speed
Setting
Set the idle speed to 925 +/- 50 rpms
with the idle screw on the throttle
housing.
(1)
Exhaust Gas
Mixture
Set the CO readings to 0.5% to 1.2%
with a CO meter. If the concentration is
too high, then turn the bypass screw in
the air flow sensor ½ turn
counterclockwise. Perform this step in
multiple sequences to get the CO
readings to an acceptable level.
(1)
Air Intake
System
1. The air intake system must be free
of leaks. Check the intake manifold,
hoses and associate components with
soapy water to determine if leaks are
occurring.
Auxiliary Air
Device
1. Verify that the auxiliary air device is
closed when the engine reaches its
normal operating temperature.
2. Clamp one of the hoses coming out
of the auxiliary air device closed and
determine if the engine speed dropped.
3. If the rpms dropped, then the
auxiliary air device is not closing
completely.
4. The valve may be visually inspected
with the engine running by using a
mirror and a flashlight.
Cold Start
Valve
1. Check the cold start valve for leaks
by clamping the fuel hose shut and
determine if the engine starts running
evenly.