Question about 2000 Ford F250 Super Duty Crew Cabs

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2000 F-350 Super Duty Idle up

I know there is a wiring harness somewhere, that will allow me to run 12 volts to a wire to increase my idle speed. Does anyone know where or what color the wire is?

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Your idle is adjusted according to your ecm if you use a 12 volt spike to try and adjust it you will spike the ecm and damage it. you can use a scan tool to adjust through the ecm...( a new ecm cost about 1500.00 bucks so word to the wise don't use a voltage lead. p[lease rate this

Posted on Sep 03, 2008


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Which fuses would affect my idle control valve and what voltage should the wire harness show it has 4 wires.2000 dodge durango 5.2 engine

There is no one fuse that powers the idle speed control valve (AKA Air Bypass Valve). It receives its power from the electronic engine control system (known as reference) and that is controlled by the computer depending on the idle load on the engine the voltage varies. So if the system reference voltage was lost then no part of the engine control system would function.

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Nov 19, 2015 | 2000 Ford F350 Super Duty Super Cab

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1999 Ram 3500 Wagon with 5.9L has eng Lt on. Idles high at red lights & surges at times. Code scanned is P0505. Do I need idle control valve or computer to make control valve work properly.

The IAC stepper motor is mounted to the throttle body, and regulates the amount of air bypassing the control of the throttle plate. As engine loads and ambient temperatures change, engine rpm changes. A pintle on the IAC stepper motor protrudes into a passage in the throttle body, controlling air flow through the passage. The IAC is controlled by the Powertrain Control Module (PCM) to maintain the target engine idle speed.

At idle, engine speed can be increased by retracting the IAC motor pintle and allowing more air to
pass through the port, or it can be decreased by restricting the passage with the pintle and diminishing the amount of air bypassing the throttle plate.
The IAC is called a stepper motor because it is moved (rotated) in steps, or increments. Opening the IAC opens an air passage around the throttle blade which increases RPM.

The PCM uses the IAC motor to control idle speed (along with timing) and to reach a desired MAP during decel (keep engine from stalling).

The IAC motor has 4 wires with 4 circuits. Two of the wires are for 12 volts and ground to supply electrical current to the motor windings to operate the stepper motor in one direction. The other 2 wires are also for 12 volts and ground to supply electrical current to operate the stepper motor in the opposite direction. To make the IAC go in the opposite direction, the PCM just reverses polarity on both windings. If only 1 wire is open, the IAC can only be moved 1 step (increment) in either direction. To keep the IAC motor in position when no movement is needed, the PCM will energize both windings at the same time. This locks the IAC motor in place.

In the IAC motor system, the PCM will count every step that the motor is moved. This allows the
PCM to determine the motor pintle position. If the memory is cleared, the PCM no longer knows the position of the pintle. So at the first key ON, the PCM drives the IAC motor closed, regardless of where it was before. This zeros the counter. From this point the PCM will back out the IAC motor and keep track of its position again.

When engine rpm is above idle speed, the IAC is used for the following:
  • Off-idle dashpot (throttle blade will close quickly but idle speed will not stop quickly)
  • Deceleration air flow control
  • A/C compressor load control (also opens the passage slightly before the compressor is engaged so that the engine rpm does not dip down when the compressor engages)
  • Power steering load control
The PCM can control polarity of the circuit to control direction of the stepper motor.

  1. First, try removing the IAC Valve, and cleaning the valve and the opening in the throttle body where the IAC Valve installs using Carburetor Cleaner. Ensure that the IAC Valve hole in the throttle body is not clogged, and is free from carbon deposits, etc. Have the ECM reset and check for the problem again.
  2. If the Check Engine Light comes back on, replace the IAC Valve. Have the ECM reset and check for the problem again.
  3. If the Check Engine Light still comes on, although highly unlikely, you may have a clogged throttle body, faulty wiring or connector, or faulty ECM (very unlikely since the vehicle runs).

Apr 13, 2011 | 1999 Dodge Ram

1 Answer

2006 F250 Super Duty starts fine no lights or problem however recently it started to miss at idle and around 2000rpm. Oil changed this week and has proggressively gotten worse and now idle is very rough...

I'm not sure of engine liter size? How long since a tune-up? I always check for codes, even if lite isn't on. Some of the national brand auto stores will check codes for free, if there are any, just tell them your lite has been going on and off.
Use a gage and check proper fuel pressure. I can give you fuel pressure spec because I don't know liter size of engine? Some vehicles don't have Schrader valve on fuel rail, which makes checking fuel pressure a little awkward.
If you have electronic returnless fuel system, you have a fuel pressure sensor, hopefully on the fuel rail. The yellow wire should be for fuel pressure, engine idling, use digital multimeter on yellow wire. 3 volts = 43.75 psi. 2 volts about 20 psi less. 4 volts about 20 psi more, so you get the picture.
The basics for a rough idle, check for a leak of some kind, fuel--egr--vacuum leak.

Oct 30, 2017 | 2006 Ford F-250 Super Duty

1 Answer

Diagnostics test says idle air control underspeed error? how do i fix 1999 ford explorer

change the idle air control valve.

Idle Air Control (IAC) Valve OPERATION The Idle Air Control (IAC) valve controls the engine idle speed and dashpot functions. The valve is located on the side of the throttle body. This valve allows air, determined by the Powertrain Control Module (PCM) and controlled by a duty cycle signal, to bypass the throttle plate in order to maintain the proper idle speed. Fig. 1: Typical Idle Air Control (IAC) valve which is mounted to the throttle body - cutaway view shows air bypass direction 89684g16.gif
  1. Disconnect the negative battery cable. To remove the IAC valve, first disconnect the negative battery cable, then the IAC wire harness plug 89684p03.jpg
    Next, remove the two IAC valve attaching bolts . . . 89684p04.jpg
    . . . and pull the valve from the intake manifold 89684p05.jpg

  2. Disengage the wiring harness connector from the IAC valve.
  3. Remove the two retaining screws, then remove the IAC valve and discard the old gasket. To install: When installing the valve, always discard the old gasket and install it using a new one 89684p06.jpg

  4. Clean the IAC valve mounting surface on the throttle body of old gasket material.
  5. Using a new gasket, position the IAC valve on the throttle body. Install and tighten the retaining screws to 71-106 inch lbs. (8-12 Nm).
  6. Attach the wiring harness connector to the IAC valve.
  7. Connect the negative battery cable.
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Oct 15, 2010 | 1999 Ford Explorer

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Intermittent: car will not accelerate when cold. No diagnostic code

1. Inspect the 2 wire harness for the 7x Crankshaft Position (CKP) sensor in the rear of the block.

2. Wiggle tug test the harness and inspect the harness for being melted from the exhaust manifold. Tests/Procedures: 1. Verify fuel pressure climbs to over 40 PSI during cranking and reads about 35-40 PSI at idle. Potential Causes: Insufficient Fuel Pressure
Tech Tips: The Powertrain Control Module (PCM) will idle the engine at a normal speed when the Throttle Position Sensor (TPS) voltage returns to the learned base idle value. This is also called 0% throttle angle. If this throttle angle is 1% or more at idle, the PCM will assume the engine is actually off idle and raise the engine speed to prevent a deceleration stall. Note that another sensor using the same 5 volt reference as the TPS can momentarily glitch the reference voltage low. This will cause the TPS to send a lower base idle voltage to the PCM, which the PCM quickly records as the new learned base idle voltage. When the reference voltage returns to 5 volts, the base TPS signal voltage increases to it's previous value. The PCM now interprets this as being off idle. This will cause the throttle angle to increase to 1% (or more) and idle the engine at a fast speed

Oct 13, 2009 | 1998 Pontiac Grand Am

1 Answer

Idele / mixture screw adjustments

You'll need a handheld tachometer or tach/dwell meter if your car does not have a tachometer.

Start by adjusting the idle screw to the correct speed (do this with the car running) allow a few seconds between adjustments for changes to take effect. I don't know the specific speed for your car, but 800-900rpms is a good catch-all setting.

Next adjust the mixture screw open. Your idle speed will gradually increase as you open the mixture screw. Again, allow a few seconds between adjustments to check the results. I like to count the turns of the screw as I make them. I will usually make adjustments 1/4 turn at a time and count, so that if I adjust too far I can go back to a setting that I know worked.

Continue to adjust your mixture until it no longer causes the idle speed to increase, then take it back about 1/8th of a turn.

Now readjust your idle screw back down into the 800-900 range.

A word of advise before you start- carb tuning is pretty much last resort when troubleshooting your vehicle. In order, you should make sure all of the following is done first:

Visually inspect all vacuum lines for cracks, holes, or disconnections.

Check ignition components (plugs, wires, etc) I will check the wires by letting the car idle and misting water around the wires. (using an old pump hairspray bottle or water bottle, etc) Watch for a little fireworks show. This is easiest to see when it is at least partially dark in your work area.

Next check to make sure your ignition timing is within spec.

Apr 05, 2009 | 1988 Toyota Corolla 4 Door

1 Answer


Your ford has power assisted breaks this power is delivered from the motor, at the point when the accelerator is inactive. There for it sounds like your idle speed setting is too low, if you have a rev counter then it should be reading around 1000 revs at idle, if not the idle needs increasing. Hope this helps

Sep 28, 2008 | 2007 Ford F-250 Super Duty Lariat

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