7
CHOKE
The CHOKE adjustment knob allows the user to adjust the amount of fuel enrichment while the engine is warming up 20% above or
below the value set at the factory. Rotating the adjustment knob clockwise will increase the amount of fuel added while the engine is
warming up. Rotating the adjustment knob counter-clockwise will decrease the amount of fuel added while the engine is warming up.
The CHOKE adjustment knob
DOES NOT
control the length of time that the fast idle solenoid is on.
BEFORE STARTING THE ENGINE:
DANGER! NEVER MAKE ANY ADJUSTMENTS TO THE POTENTIOMETERS ON THE FRONT OF THE DIGITAL ECU WHILE THE
VEHICLE IS IN MOTION. BE SURE THAT THE VEHICLE IS IN PARK OR NEUTRAL WITH THE PARKING BRAKE
SET. FAILURE TO DO SO MAY RESULT IN PROPERTY DAMAGE, PERSONAL INJURY, AND/OR DEATH.
WARNING! The adjustment knobs on the front of the ECU are precision manufactured parts and do not require a great deal
of force to turn. Do not apply excessive force to the adjustment knobs. Full adjustment range for the knobs is 3/4
of a turn.
1. After all electrical connections have been made, double-check all connections to ensure that they are tight and secure.
2. Reconnect the battery.
3. If installed, remove the oxygen sensor harness from the digital ECU by unplugging the harness from the rear of the ECU.
4. Although the adjustment potentiometers on the front of the digital ECU were set at the factory in the null position, check to ensure
that they were not moved. If necessary, rotate the potentiometers so that they are positioned as shown in Figure 3.
5. Turn the ignition key to the “RUN” position. DO NOT START THE ENGINE. Listen for the fuel pump. The fuel pump should run
for several seconds before shutting off.
6. Turn the ignition key to the “OFF” position.
Adjustment Potentiometer Settings for Initial Startup
Figure 3
SETTING THE MECHANICAL IDLE:
The setting of the mechanical idle speed is critical in the operation of the Digital ECU and is best accomplished by using a tachometer.
If your vehicle is not equipped with a tachometer, Holley highly recommends one be used. To adjust, follow the instructions carefully.
1. Disconnect the yellow wire from the fast idle solenoid by unplugging the female quick disconnect terminal from the tab at the base
of the solenoid.
2. Start the engine. With the engine running at idle, insert a flat blade screwdriver into the head of the idle adjustment screw located
on the front of the throttle body on the driver’s side of the vehicle.
3. Turn the idle adjustment screw clockwise to increase the engine idle speed, or counterclockwise to decrease the engine idle speed,
until the engine speed is approximately 750 to 800 rpm.
4. Have another person depress the brake pedal and set the parking brake. Put the car in gear (automatic transmissions only) and
allow the engine speed to stabilize while continuing to apply both the brakes and the parking brake. Turn the air conditioning on
high, if so equipped, and turn on your high beam lights.
5. Adjust the idle adjustment screw until the engine speed is set at approximately 700 rpm.
