ENGINE DIVISION SERVICE MANUAL TM 5-4210-230-14&P-1 observe the following additional precaution: Idle   mixture   adjustments   must   be   made   as   soon   as possible after engine wi1ll run without choke (choke plate fully open) before sufficiently high to cause evaporation of winter grade gasolines.  Enrichment of the idle mixture by fuel evaporation can be detected by observing test meter readings.   Readings   should   remain   stable.      A   gradual increase in engine idle speed (RPM) or a tendency for the CO   meter   to   climb   toward   the   rich   side   without   any adjustments   being   made   indicates   a   richening   of   the mixture   due   to   fuel   evaporation.   When   this   condition occurs,  engine  should  be  allowed  to  cool  before  making final mixture adjustments. Setting 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). Fig.  59 Exhaust Analyzer - SE-2507 b. Disconnect air injection hose(s) at air manifold check valve(s) and plug air manifold check valve(s). c. Operate   engine   until   it   reaches   normal   operating temperature (unless winter grade gasoline is used). d. Adjust     curb     idle     speed     to     specifications     (see Emission Control System Tune-Up Specifications). e. Prepare   Exhaust   Analyzer   SE-2507   or   equivalent, and  insert  exhaust  sample  probe  into  vehicle's  tail pipe (refer to test equipment manufacturer's instructions for preparation and hook-up procedures. f. Observe percent of carbon monoxide (%CO) indicated   on   analyzer   dial   and   adjust   idle   mixture screw(s)     to     obtain     specified     CO     setting     (see Emission Control System Tune-Up Specifications), if necessary. g. Readjust    idle    speed,    if    necessary,    and    readjust mixture screw(s) to provide the specified CO setting at the specified speed. h. If specified CO setting cannot be obtained, establish proper mixture screw(s) setting as follows: (1)    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. (2)    Gently seat idle mixture screws. (3)    Adjust    idle    speed    and    mixture    screw(s)    (equal number of turns) to provide the specified CO setting at the specified speed. (4)    Install  new  plastic  (service  limiter  cap(s)  with  tab  in the mid-position. i. Disconnect test equipment from engine and reconnect  air  injection  hose(s)  to  air  manifold  check valve(s). Adjustment Procedure without Exhaust Analyzer. For U.S.A.  (except California) and Canada engines. Idle  speed  and  fuel  mixture  adjustments  must  be  made with parking brake applied, air cleaner in place, transmission in neutral and air conditioning "OFF". CGES-215  Page 33 PRINTED IN UNITED STATES OF AMERICA