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ENGINE DIVISION SERVICE MANUAL
TM 5-4210-230-14&P-1
To compensate for fuel and temperature variations when
setting idle mixture, observe these precautions:
a.
Do not idle engine continuously for more than three
minutes at one time.
b.
After each three minutes of idling, increase engine
speed to 2000 rpm for one minute.
c.
Continue with idle adjustment procedure. Do not idle
engine for more than three minutes without repeating
Step b.
Adjustment Procedure:
a.
Connect tachometer to engine. (Tachometer should
have an expanded scale of 400 to 800 or 0 to 1000
rpm and 1 to 2% accuracy.
b.
Remove limiter cap(s). To prevent damage to screw
threads or seat, file or grind away the side of the cap.
Do not pry cap off.
c.
Operate engine until it reaches normal operating
temperature.
d.
Gently seat idle mixture screws (not required on 4-
196 engine).
e.
Carefully, adjust idle mixture screws (equal number
of turns) to produce maximum idle speed.
f.
Observe tachometer and adjust curb idle screw to
obtain the following required engine speed. Required
engine speed is the total of the midrange of Curb Idle
Speed
(see
Emission
Control
Tune-Up
Specifications) and Speed Drop RPM (see Emission
Control Tune-Up Specifications) added together.
g.
Adjust curb idle mixture screw(s) (equal number of
turns) in until mid-point of idle speed range
specification is obtained (see Emission Control
System Tune-Up Specifications).
h.
Install new plastic (service) limiter cap(s) with tab in
mid-position.
CGES-215 Page 34
PRINTED IN UNITED STATES OF AMERICA
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