Computers and Control Systems: Adjustments

NOTE: Incorrect ignition timing can cause idle speed changes. Conversely, incorrect idle speed can affect the ignition timing. Ignition timing and idle speed should be adjusted concurrently.

CURB IDLE SPEED
1. Confirm initial inspection conditions:

a. Engine coolant temperature is 185 - 205°F.
b. Lights, cooling fan and all accessories are OFF.
c. Transaxle is in neutral or park.
d. Steering wheel is in straight-ahead position, (on vehicles with power steering).
2. Check the ignition timing and adjust, See Adjustment Procedures.

Tachometer Connection:

3. Connect the pick-up lead of a tachometer to the connector.

4. Start the engine and operate at 2500 rpm for more than 5 seconds and then at idle for 2 minutes.
5. Check the engine idle speed. If it is NOT within specifications, check the idle speed control system.

Curb Idle Speed:
750 ± 100 RPM

6. Stop engine and disconnect tachometer (if further adjustments are required, do not disconnect the meter).

Ignition Timing Adjustment Hook-up:

IDLE SPEED CONTROL (ISC) SYSTEM
1. Remove the protective cap from the ignition timing adjustment connector.
2. Using a suitable jumper, connect the terminal to ground.

Idle Speed Adjustment Jumper Wire:

3. Using a suitable jumper wire, ground the #10 terminal in the self-diagnosis connector.
4. Start the engine and warm to operating temperature and check the idle speed.


Basic Idle Speed:
750 ± 100 RPM

5. If necessary, adjust to the specified speed by turning the speed adjusting screw.

NOTE
^ The engine speed may be slightly lower on a new engine (less than 300 miles) in which case, no adjustment is required.
^ If the engine speed is low, there is a possibility of carbon deposits on the throttle valves assembly.
^ If the idle speed is too high and normal adjustments do not bring the speed within range, there is a possibility that the fast - idle air valve has an internal leak. If so, this will require replacement of the throttle chamber.