Toyota 4-Runner 1985 Repair Manual page 268

FUEL SYSTEM - Carburetor
Idle Mixture
ADJUSTMENT OF IDLE MIXTURE
NOTE:
FU-25
• To conform with regulations, the idle mixture adjusting
screw is adjusted and plugged with a steel plug by the
manufacturer.
Normally, this steel plug should not be removed.
• When troubleshooting rough idle, check all other possi-
ble causes before attempting to adjust the idle mixture.
(See TROUBLESHOOTING on page FU-2)
Only if no other factors are found to be at fault, should
the idle mixture be adjusted and, when doing so, remove
the plug and follow the procedure described below.
1. REMOVE CARBURETOR
(a) Before disconnecting the vacuum hoses, use tags to
identify how they should be reconnected.
(b) Remove the carburetor from the engine.
(c) After removing the carburetor, cover the intake
manifold with a clean rag.
2. REMOVE MIXTURE ADJUSTING SCREW PLUG
(MAS PLUG)
(a) Plug each carburetor vacuum port to prevent entry of
steel particles when drilling.
(b) Mark the center of the plug with a punch.
(c) Drill a 6.5mm<t> (0.256 in.<t»hole in the center of the
plug.
NOTE:
• As there is only 1 mm (0.04 in.) clearance between the
plug and screw, drill carefully and slowly to avoid drill-
ing onto the screw.
• The drill may force the plug off at this time.