Carburetor engines
On carbureted engines, the idle speed should be checked with the engine normally warm and the fast idle system not engaged. Connect an external tachometer or use the stock one on the dashboard; the onboard one is at least as accurate as the outside one.
Adjustments are made with the idle adjustment screw located on the carburetor. This is a mechanical adjustment that just slightly either opens or closes the throttle, thus changing the idle speed. On the Accord, the throttle lock has a knurled plastic head to make adjustments easier. The head, however, is located on the baffle side of the carburetor and may be difficult to access. The spring on the regulator also makes it difficult to turn the detent.
On the Prelude, the dual carburettor arrangement uses a vertically mounted screw acting on the throttle linkage. The screw is placed between two carburetors.
WARNING: Especially on the Prelude, but not the Accord either, be sure you find the correct screw before you start adjusting. Screws on the link mechanism sealed with paint, usually yellow, must NOT be used. These are the factory controls.
Injection engines
1985 Accord SEi
1. Start the engine and warm it up to normal operating temperature; the cooling fan should start at least once.
2. Connect a suitable tachometer using the manufacturer's instructions.
3. Check idle speed with all equipment off.
To eliminate the operation of the control system x.x., pull off the vacuum hose #27.
4. The idle speed should be 750±50 rpm (in neutral). Adjust the idle speed, if necessary, by turning the idle adjustment screw.
5. Check the controller х.х., which increases the speed when the air conditioner is on. The idle speed should be 800±50 rpm (in neutral).
6. Adjust the idle speed, if necessary, by turning the adjusting screw B.
1986-91 ACCORD and PRELUDE
1. Start the engine and warm it up to normal operating temperature; the cooling fan should run twice.
2. Connect the tachometer.
3. On 1986-87 Accord and 1984-87 Prelude, disconnect the top vacuum hose to the idle control solenoid valve (between valve and intake manifold) from the intake manifold. Close the ends of the hose and intake manifold.
4. On 1988-91 vehicles, disconnect the 2-pin EACV connector.
5. With all accessories disabled, check the idle speed. The idle speed should be 750±50 rpm (in neutral). Adjust the idle speed, if necessary, by turning the idle adjusting screw.
6. Turn the ignition key to the OFF position (disabled).
7. Reconnect the connector, then remove the CLOCK fuse in the fuse box under the hood for at least 10 seconds; this will reset the ECU settings.
8. Check the idle speed with the heater blower switch in position "HI" and the air conditioner turned on. The idle speed should be 750±50 rpm (in neutral). Adjust the idle speed, if necessary, by turning the adjusting bolt on the air conditioning idle boost valve.
9. After adjustment, connect the idle control solenoid valve vacuum hose.
10. On automatic transmission models, after adjusting the idle speed, check that it stays within the specified limits when the engine is shifted into gear. The idle speed should be 750±50 rpm.
11. Check idle speed with all accessories on and A/C off. The idle speed should remain 750±50 rpm.