Opel 1900 1973, Service Manual, Page: 341 / 625

50 1973 OPEL SERVICE MANUAL
MAINTENANCE AND ADJUSTMENTS
IDLE SPEED ADJUSTMENT
Note:
Idle speeds of to are normal
for engines with less than miles.
Prior to making any adjustment to the carburetor,
the following items must be checked for proper oper-
ation and/or setting:
1. Valve Adjustment (Hydraulic lifters can be im-
properly adjusted.)
2. Dwell Angle.
3. Ignition Timing.
4.
Spark Plug Gap.
5. Exhaust Gas Recirculation Valve (See “Check-
ing” under EXHAUST GAS RECIRCULATION
SYSTEM.)
After it has been ascertained that the above items are
properly adjusted and operating correctly and idle
R.P.M. is still not within specifications, proceed as
follows:
1. With air cleaner installed, run engine until normal
operating temperature is reached.
2. Remove plastic caps from the idle mixture screw
and air speed screw. See Figure
Figure 1 Carburetor Adjusting Screws
3. To raise R.P.M., turn air speed screw counter-
clockwise. To lower R.P.M., turn air speed screw
clockwise, thereby reducing the amount of air going
through the system.
4. idle mixture screw until highest R.P.M. is
obtained. Alternately adjust idle mixture screw and
air speed screw until R.P.M. is obtained that is 50
R.P.M. higher than the desired final setting. This is
to be accomplished with the idle mixture screw at
best idle.
5. Turn idle mixture screw clockwise (lean) until a
decrease of 50 R.P.M. is obtained. The idle R.P.M.
will
be within specifications and proper emis-
sion control maintained.
6. Install red plastic caps over the air s p e e d s c r e w
and idle mixture screw.
Basic Idle Adjustment
A basic idle adjustment is to be made only if engine
idle R.P.M. correction does not result in correct idle
R.P.M. setting and engine has more than
miles
of operation. If necessary, proceed as follows:
1. Remove plastic cap from the throttle valve stop
screw. See Figure
2. Place the Manometer (J-23951) in a vertical posi-
tion. Turn the 2 vents on top open to equalize pres-
sure and balance gauge to read zero. With engine
idling, unplug the vacuum advance hose from the
carburetor and connect the manometer hose in its
place. See Figure 12.
Figure Throttle Plate Calibrator J-23951
Installed
3.
If the manometer does not read 1 to 8 inches of