See Figure 1
Normal idle speed is controlled by the SMEC. This adjustment is the minimum idle speed with the Automatic Idle Speed (AIS) motor closed.
Before adjusting the idle on an electronic fuel injected vehicle the following items must be checked.
- AIS motor has been checked for operation.
- Engine has been checked for vacuum or EGR leaks.
- Engine timing has been checked and set to specifications.
- Coolant temperature sensor has been checked for operation.
- Connect a tachometer and timing light to engine.
- Close AIS by using ATM tester C-4805 or equivalent, ATM test code #03.
- Connect a jumper to radiator fan so that it will run continuously.
- Start and run the engine for 3 minutes to allow the idle speed to stabilize.
- Check engine rpm and compare the result with the specifications listed on the underhood emission control sticker.
- If idle rpm is not within specifications, use tool C-4804 or equivalent to turn the idle speed adjusting screw to obtain 800 +- 10 rpm. If the underhood emission sticker specifications are different, use those values for adjustment.
If idle will not adjust down check for binding linkage, speed control servo cable adjustment or throttle shaft binding.
- Turn off the engine, disconnect tachometer, reinstall AIS wire and remove jumper wire from fan motor.