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Idle Reset Procedure


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#1 BobCat

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Posted 10 July 2005 - 09:29 PM

Idle Reset Procedure
Here is the correct procedure to set and adj the idle. No guess and check crap and it works 100% of the time.

1. Disconnect the battery terminals to reset/clear the computer's memory. Leave it disconnected for 30 minutes. WARNING: Whenever removing your battery cables ALWAYS disconnect the negative battery cable first and reconnect it last. Otherwise you could destroy your computer or cause a battery explosion.
2. Disconnect the plug going to your idle motor which is located on the front of your throttle body.
3. Reconnect your battery's positive and then negative terminal.
4. Start the engine, and set the idle to the rpm you want with the stop screw on the bottom of the throttle body around 750-800rpm is factory spec.
5. Turn off the engine.
6. Check the TPS and adj. the voltage if necessary to be btw .94-.98V with the Key On Engine Off.
7. Reconnect the plug on the idle motor
8. Make sure all accesories (radio, blower motor, a/c, lights, etc) are off and start the engine.
9. Let engine run for two minutes.
10. Turn engine off and wait two minutes then restart engine and let idle for two minutes with all accesories on.


Take a look at this link and it explains cleaning the IAC adj. the TPS and a few other things to fix a surging idle. http://www.muscularm...gs.com/iac.html
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#2 BobCat

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Posted 30 August 2005 - 09:27 PM

An even more detailed procedure for the SN-95 cars.

Courtesy of Tom Moss "tmoss"

Setting Idle

Begin with a cold vehicle. The idea here is to get the car to a firm cold idle with enough airbleed capacity left in the idle circuit for IAC adjustment.

The idle stop should be set first. Back out the idle stop screw, away from the bell crank arm, until about 1/2 turn past the point where it no longer makes contact (blade fully closed). Using an 0.010" feeler gauge, tighten until gauge just drags between screw and bell crank arm. Remove feeler gauge. Tighten screw exactly 1 1/2 turns. If the screw is very loose, put a drop of locktite or silicone on it, so it doesn't work out of adjustment.

Now remove the connector to the Idle Air Controller (IAC) just on the other side of the throttle body. Start the car and allow to warm for 2 minutes. Give a small "blip" to let it settle. If it is having a hard time staying running you may have to get an assistant until you can get to the front of the car. Now open or close the air bleed screw (CCW opens) next to the IAC until the car idles at 575 to 600 rpm. For guys with aftermarket cams and an EEC tuner, you might want to idle a bit more briskly, say 650 to 675.

Turn off the car. Now count the number of turns clockwise to close on the idle air bleed screw. If it falls between 1/2 and 2, it's okay, now reverse it out the same number of turns. Log the number somewhere in case you need it for the future. Reconnect the IAC. You are done.

If the air bleed screw is above 2 turns, it's a good idea to tighten the idle stop screw another 1/2 turn, then repeat the idle setting. If it is below 1/2 turn, then loosen the idle stop screw by 1/4 to 1/2 a turn, and repeat the idle setting. Be sure to put another drop of silicone rtv on the stop screw if it was disturbed. Reconnect the IAC. You are done.

Checking the IAB/IAC
The Intake Air Bypass (IAB) is a solenoid (also known as an Idle Air Controller IAC) – operated air control valve used on Ford SEFI engines. The EEC controls the valve by switching its ground wire on and off at a frequency of about 60 hertz (cycles per second). That rate is high enough that the valve never closes and instead “dithers” somewhere between open and closed. The more duty cycle used, the more open the valve becomes and vise-versa. If the throttle stop is set correctly, the engine will not idle if the IAB has failed closed.

The IAB contains a diode, so if you are checking the solenoid with an ohmmeter for resistance, you should get 7-13 ohms from VPWR(+ lead) to ISC(- lead) and 0 ohms when checking ISC(+ lead) to VPWR(- lead) due to the diode. With the IAB disconnected, check resistance of each lead to the IAB case for shorts – resistance should be high and any reading of 0-13 ohms indicates a short to the case – replace the IAB.

In the car with the ignition on, you should have 12v to both wires until the EEC starts to “dither” and then the voltage will come down. If it does not, then the solenoid winding may be open and be an indication of a bad IAB.

You can use an old dwell meter if you don’t have a multi-meter with a frequency measuring capability to check the IAB. Use straight pins through the wire jackets to make the connection to the dwell meter and set on the 4-cylinder setting. Run the engine at idle and if the dwell meter reads “0” or “90”, the EEC is not functioning correctly and needs to be replaced to restore proper idle control. Of course if you have a frequency reading multi-meter, use it to check for the EEC control of the IAB.
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