Honda Civic SiR

Honda Tips and Tricks

This page contains some of the tips and tricks that are useful for general maintenance of your Honda. At the moment there are only instructions on how to set the idle.

Set Idle

Setting the idle correctly on a Honda Civic (or any Honda) is important. If the idle is not set correctly the car will either idle too low, or it will idle too high causing the idle to surge up and down.

Instructions to set the Idle

Warm the car up to operating temperature. This is generally determined when the radiator fan turns on if the car is stationary.
Unplug the IACV valve on the back of the intake manifold. This needs to be done because the IACV valve is what the ECU uses to dynamically control the idle by allowing more or less air to bypass the throttle plate. Be careful not to burn yourself!
Set the idle to 600rpm using the idle control screw. This screw controls the static amount of air that bypasses the throttle plate.
Turn the car off and plug in the IACV valve.
Reset the ECU. This needs to be done because the ECU will have thrown an ECU error code.
Restart the car. The idle should be running nice and close to 750rpm.

There are other things that can affect the idle, but these are much less likely.

The throttle plate is worn or is not closing far enough and and is letting too much air past. If this is the problem then you would not have been able to adjust the throttle down to 600rpm with the IACV valve unplugged. Check the adjustment of the throttle stop to make sure that the throttle plate is closing enough.
The voltage of the throttle position sensor is not correct. It should read 0.5V when the throttle is closed and 4.5V at WOT. This is not easy to test. Refer to your Honda Service Manual for instructions.
Other gremlins, which I haven't remembered...