Idle Surge (I've searched and read everything .. now what?)
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From: Branford, CT, 06405
Idle Surge (I've searched and read everything .. now what?)
I have cleaned the IACV a bunch of times and when we took it apart the other day we diagnosed it and it is doing its job. Somehow by adjusting the idle screw lower with the EVAP connector disconnected (b/c the Helms says to adjust idle this way) I have gotten rid of the surge at idle but funny enough if I rev the car over 2K and hold the throttle there the surge still happens. If I hold it at 3k the surge still happens, but after 3500 it goes away? WTF?!?!?!?!?
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Joined: Jun 2005
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From: Tachikawa Shi, Tokyo, Japan
Re: Idle Surge (Excelerate)
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 fluxuates because the ECM sees that the idle goes up to a certain limit and that the speedo is at zero, so the computer cuts the fuel injection off and when the idle drops to a certain limit it turns the injectors back on again and the entire cycle keeps repeating itself over and over again and again.
Duane in Japan
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 fluxuates because the ECM sees that the idle goes up to a certain limit and that the speedo is at zero, so the computer cuts the fuel injection off and when the idle drops to a certain limit it turns the injectors back on again and the entire cycle keeps repeating itself over and over again and again.
Duane in Japan
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Markb16a
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