My idle keep going up and down. Some times it feel like the engine is going to turn off. When I am in waiting for the red light to turn gree my idle goes to 1 and 1 1/2. Please give me a solution to fix these problem.

 

Here is a start.

High Idle speed and Fluctuation troubleshooting

Leaking EACV- Disconnect EACV connector. Idle speed should decrease. With the connector disconnected block the hole in the intake port or pinch the hose from the air cleaner to the EACV. If the idle speed decreases the valve is leaking. This condition will not set a code. The ECM can only detect an open or short circuit. It also may clog it’s screen if it has one.

Leaking IAC- (Idle air control valve) Disconnect IAC connector. Idle speed should decrease. With the connector disconnected, block the hole or pinch the hose to the IAC valve. If the idle speed decreases the valve is leaking. May not set a code and may not be a codeable circuit on all models.

TW or ECT sensor- (engine coolant temperature sensor) voltage should be about 3.0 volts @ 60 deg F and between .55 & .7 volts @ normal operating temp. If the voltage is above .8 volts at normal operating temp, will cause rich mixture and high idle speed. May not set a code because it is not far enough out of its operating parameters. **Also this sensor will not read temperature correctly if coolant is low. (beware)

Vacuum leaks- a loose vacuum hose or leaking intake manifold gasket can cause high idle speed and/or fluctuation. Also check for bad PCV valve.

Fast Idle Valve- (if equipped) a fast idle valve that is sticking can cause high idle speed and fluctuation. Check it by removing the steel cap on the top and putting your finger over the hole in the middle of the seat under the cap or block the port just inside of the throttle body opening, when the Idle is fluctuating or staying high. When the engine is warm this valve should be closed. You can tighten the seat but it will also change the idle speed warm up values (closing).

Throttle valve- throttle position sensor voltage should be .5 volts with the throttle closed. Make sure the throttle valve is fully closed and voltage is within spec.

ECU-If all else is good, if you reset the ECU and the problem goes away temporarily, the ECU may be defective.

The idle fluxes due to the fuel control programming built into the ECU, it notices that the engine is going too fast and that there is no VSS signal to the speedo, so the ECU cuts the fuel to the injectors to eliminate a higher than normal idle speed since the vehicle is not moving. Once the idle drops to a predetermined level the fuel injectors are turned back on and the vicious cycle starts all over again.

If there is air in the cooling system, it may be trapped at the engine coolant temperature sensor and the computer does not know what the coolant temp is but it knows that the engine bay is hotter now and that the O2 sensor is working so it goes bananas trying to keep things going, air may be trapped in the idle control valve, the one with two black small rubber hoses going in and out of it, there is also a screen in there that tends to get dirty and plugged, I have seen pics on H-T before of the parts break down but it didn’t show this screen with the rubber O-ring type gaskets, it is available with the O-ring kit here in Japan.