Question about 1998 Ford F150 Regular Cab

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Wiring diagram for 98 f-150 4.2L Idle air control valve. Repaced IAC but still gets same code & stalls after surging.

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6ya6ya
  • 2 Answers

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Posted on Jan 02, 2017

jonbrown725
  • 73 Answers

SOURCE: 1987 F 150 Problem: engine idle stalling and then surges

Here is a idea, there is a small rubber tube connected to the bottom of the throttle body, it is a vacuum line. It is located under the breather hose where it connects to the intake. This tube is located near the Throttle Positioning Sensor, If it is cracked or has come off, it will make the engine surge.

Posted on Jan 14, 2009

  • 25 Answers

SOURCE: stalling no idle

Hi,if you want to now where is a leak ,start the car if is possible and spry the hosing pipes wen suddenly rpm increase you now where is the problem or ken be the trottle body!

Posted on Jan 16, 2009

  • 19 Answers

SOURCE: 1997 buick lasabre custom high idle, transmission, stalling

had same problem i would check the Idel Air Valve and also check all of your vaccum hose lines makeing sure there are no cracks or splits in rubber connectors if there is repair immediatelt because over time they start to dammage the internal parts fo the engine and if youve replace tps mass air etc. sounds like a vaccum hose problem

Posted on Feb 10, 2009

emissionwiz
  • 75130 Answers

SOURCE: fast idle after warm up .already changed IAC valve

fast idle is many times caused by a engine intake vacuum leak, use a can of carb spray and spray the top of the engine for leaks, if u hit one u will hear the eng change idle speed, also look for split or leaking vacuum hoses.

Posted on May 20, 2009

Molson02536
  • 3854 Answers

SOURCE: IAC Valve Location - 1996 Jeep Grand Cherokee

The idle air control valve is located on the back of the throttle body. It has an oval electrical connector and two torx screws holding it in. Unplug the connector, remove the two screws then lightly tap the body with a soft faced mallet to loosen it from the body. 
Once you have it out and prior to installing a new valve clean the seat inside the throttle body where the idle control fits. This must be very clean! Installation is in the reverse order. 
 To save some cash, pull the valve out and clean it with throttle body cleaner, this usually fixes the problem for quite a while.
Good luck and hope this helps.

Posted on May 28, 2009

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1994 ford escort wagon lx 4cyl standard won't idle, dies at stops. Had idle throttle sensor and throttle sensor replaced. Doesn't help even though when coded it said that was the problem. Help!


The DTC - diagnostic trouble code may have had the word IAC - idle air control etc.... that doesn't mean the valve is bad . The IAC has electrical circuits associated with it . There could be an open circuit , short to ground , short to power etc.... The Idle air control passage could be plugged . How To Fix Car That Idles Poorly Clean the IAC
Ford idle air control valve IAC test stalling problems

May 06, 2017 | Ford Cars & Trucks

1 Answer

How do you fix an idleing problem on b2300 mazda truck?


What kind of idling problem ? An what year Mazda ? Idle is controlled by the engine computer via a IAC motor , idle air control valve or motor, what ever Mazda calls there set up ! Or if a fairly new vehicle, they use drive by wire or electronic throttle control . With the idle air control set up passages get plugged an don't allow enough air to by pass the throttle plate causing stalling problems . A vacuum leak can cause a ruff unstable idle an stalling also . A dirty throttle plate can cause idle problems as well ! A scan tool ,not a code reader is a very use full tool to check engine data parameters. With the scan tool you can view idle air control counts . To see if the engine computer is actually controlling the idle air control valve . Idle Air Control Valve

Also an engine misfire can cause idle problems , also clogged fuel injectors can as well . A good diagnostic technician would start with hooking up a professional grade scan tool , checking for DTC'S - diagnostic trouble codes , misfire data , engine sensor data , IAC counts ! Section 20 Idle Speed Controls lecture preview

Oct 02, 2015 | Mazda Cars & Trucks

1 Answer

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.

Solutions:
  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

When i turn on the ac the idle goes low and the the car vibrates. When i turn off the ac the car stop vibrating.



Operation

The Idle Air Control (IAC) valve controls the amount of air that bypasses the throttle valve, which controls the engine idle speed. The IAC valve consists of windings, an armature, a return spring, and a rotary slide. The engine control module (ECM) pulses the voltage to the winding, the opposing forces on the armature by the return spring cause it to maintain a fixed position, adjusting the amount of bypass air to maintain the correct idle speed.


Removal & Installation

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the idle air control valve harness electrical connector.
  3. Using a suitable tool, remove idle air control valve.
  4. Installation is in reverse order of removal.


Testing

Checking Idle Air Control Valve (IAC) Triggering

  1. Check IAC valve is electrically OK.
  2. Slide up boot on the IAC valve connector.



0900c152801c00a1.jpg enlarge_icon.gifenlarge_tooltip.gif

Fig. IAC Connector

  1. Use scan tool 'Output Diagnostic Test Mode' function 03 to trigger the IAC valve - N71.
  2. Connect VAG 1527B voltage tester, or equivalent, between terminal 1 and engine ground (GND). Voltage tester must flash.
  3. Connect VAG 1527B voltage tester, or equivalent, between terminal 2 and battery positive voltage (B+). Voltage tester must light up.
  4. If specified results are not obtained:
    1. Connect VAG 1598/19 test box, or equivalent, to ECM harness connector.
    2. Check the wiring between harness and connector terminal 1 (in engine compartment) to test box socket D11 . Then check the wiring between harness connector terminal 2 and test box socket D9 using wiring diagram. Repair as necessary.
    3. If the wiring is okay, but triggering still does not occur, replace the ECM.
    4. If the triggering signal and the wiring are okay and the valve does not react, replace the IAC valve.


Checking Mechanical Function
  1. Remove the idle air control (IAC) valve.
  2. Visually check the surface of the rotary slide (arrow) for signs of wear.



0900c152801c00a2.jpg enlarge_icon.gifenlarge_tooltip.gif

Fig. Showing the IAC Valve

WARNING Do NOT check for ease of movement by prying on the rotary slide with a screwdriver or other tools that could cause scratching or other damage.

  1. Reconnect the IAC valve, while still removed, to the harness connector.
  2. Use scan tool 'Output Diagnostic Test Mode' function 03 to trigger IAC valve - N71.
  3. Check whether rotary slide moves freely from stop to stop.
  4. If there are signs of scoring, or if the rotary slide does not move freely in both directions, replace the IAC valve.
  5. If the IAC valve does not respond (not triggered) during the Output Diagnostic Test Mode, check triggering.

Resistance Test
  1. Remove the idle air control valve harness connector.
  2. Use a suitable Digital Multimeter (DMM) to measure the resistance between the 2 terminals of the idle air control valve.
  3. The correct measurement should be 7-11 ohms. If not, replace the idle air control valve.


NOTE At room temperature, the resistance value will be lower. The resistance value will be higher if the Idle Air Control (IAC) valve is measured at under-hood operating temperatures.
  1. Reconnect the idle air control valve harness connector.
  2. The idle air control valve should hum and vibrate slightly when the ignition is turned 'ON'. If not, the ECM or harness may be defective.

Testing with VAG1551:
  1. Remove the idle air control valve harness connector.
  2. Connect the VAG 15278 LED tester to terminals 1 and 2 of the harness connector using the jumpers from VW 1594 adaptor kit.
  3. Turn ignition ON, perform steps from output DTM (Diagnostic Test Mode) to activate the IAC valve (N71) LED tester must blink.
  4. If tester does not blink, check wiring using VAG 1598 pin out box, electrical checks, step 26. Repair as necessary.
  5. If wiring is okay, replace the ECM.
  6. If LED tester blinks but the IAC valve does not operate, replace the IAC valve.

Feb 15, 2011 | 2000 Volkswagen Jetta TDI

2 Answers

Actron trouble code PO505 99 acura


P0505 - IAC (Idle Air Control) System Malfunction

The IAC (Idle Air Control) valve controls the idle speed of the engine. At idle the throttle plate is closed, of course. The IAC is computer controlled and allows only a certain amount of air around the throttle plate. This metered air controls the idle speed. The IAC has a "plunger" or "shutter" that moves to open or close the bypass air passageway. The more air the IAC allows around the throttle plate, the higher the idle. The PCM (Powertrain Control Module) uses the IAC valve to keep the idle speed correct with varying engine demands. Can be a three or four wire sensor depending on the model.

The PCM monitors voltages of the IAC circuits and if it detects an incorrect voltage on one or more of the IAC motor circuits it will set P0505. NOTE: Problems with the IAC would only be noticeable at idle or when throttle is closed.

Symptoms may include:
* MIL (Malfunction Indicator Lamp) illumination
* Engine stalls and may not idle unless throttle is depressed
* Intermittently stalls when letting off the throttle
* Engine may idle too high


Potential causes of an P0505 code include:
* IAC motor connector is damaged (check connector and pins for damage, and moisture)
* One or more IAC circuits open or shorted to ground
* One or more IAC circuits are shorted to voltage
* IAC has failed
* PCM has failed


Possible Solutions:
This should be a fairly straightforward diagnosis. Start by clearing the fault codes. Then unplug the IAC and start the engine (This may cause other IAC codes to set. Just ignore them for now). If the P0505 code doesn't reset, replace the IAC. It is internally shorting one of the IAC circuits. If the code DOES return after unplugging the IAC and starting the engine, then you know it isn't the IAC motor. Visually check the wiring harness all the way back to the PCM. You may need to visually inspect the harness by removing all the insulation off the wires. It is possible that the wires could be shorting to eachother or to other wires in the harness.

If there are no wiring problems, and the code keeps returning with the IAC unplugged, you can check the PCM by removing the IAC wires from the PCM connector (or clipping the wires in a location where they can be repaired easily) and then start the engine (If you're not sure, don't do it. Take it to a qualified professional). Now if the code doesn't reset there is a problem with the wiring. Check for continuity on all the IAC wires. Any resistance points to a problem. Check for voltage on any(At this point there shouldn't be any voltages on the wires because they're clipped at one end and unplugged at the IAC). Repair as necessary. But if the P0505 code DOES reset after removing the IAC wires from the PCM connector(or clipping them), replace the PCM, there's a problem internally on the IAC control circuit.

Hope this helps (remember to rate and commene this).

Jan 06, 2011 | 1996 Acura TL Series

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
--- REMOVAL & INSTALLATION
  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

1 Answer

Will not idle, will run if you push on the gas and hold it. No engine light indicator


you need to clean your idle air control valve ( or replace it) Spray carb cleaner does a nice job of cleaning it.

This tutorial is from autozone.com


OPERATION



The Idle Air Control (IAC) is a bi-directional motor driven by two coils. The purpose of the IAC valve is to control engine idle speed, while preventing stalls due to changes in the engine load. The IAC valve, mounted in the throttle body, controls bypass air around the throttle plate. The PCM controls engine idle speed by adjusting the position of the IAC motor pintle. The PCM pulses current to the IAC coils in small steps (counts) to extend the pintle into a passage in the throttle body to decrease air flow. The PCM reverses the current pulses to retract the pintle, increasing air flow. This method allows highly accurate control of idle speed and quick response to changes in engine load. If RPM is too low, the PCM will retract the IAC pintle, resulting in more air being bypassed around the throttle plate to increase RPM. If the RPM is too high, the PCM will extend the IAC pintle, allowing less air to be bypassed around the throttle plate, decreasing RPM.



0900c15280217cd2.jpg enlarge_icon.gifenlarge_tooltip.gif

Fig. Typical Idle Air Control (IAC) valve components
During idle, the proper position of the of the IAC pintle is calculated by the PCM based on the battery voltage, coolant temperature, engine load and engine RPM. If the RPM drops below a specified value, and the throttle plate is closed (TP sensor voltage is between 0.20-0.74), the PCM senses a near stall condition. The PCM will then calculate a new IAC pintle position to prevent stalls.
If the IAC valve is disconnected and reconnected with the engine running, the idle RPM will be wrong. In this case, the IAC has to be reset. The IAC resets when the ignition switch is cycled ON and then OFF . When servicing the IAC, it should be disconnected or connected with the ignition switch OFF in order to keep from having to reset the IAC valve.
The position of the IAC pintle affects engine start up and the idle characteristics of the vehicle. If the IAC pintle is fully open, too much air will be allowed into the manifold. This results in high idle speed, along with possible hard starting and a lean air/fuel ratio. A Diagnostic Trouble Code (DTC) may set. If the IAC pintle is stuck closed, too little air will be allowed in the manifold. This results in a low idle speed, along with hard starting and a rich air/fuel ratio. Again, a Diagnostic Trouble Code (DTC) may set. If the IAC pintle is stuck part way open, the idle may be high or low and will not respond to changes in engine load.


TESTING



As with most all engine control sensors used in your vehicle, a thorough and proper test can only be performed by a qualified technician using a scan tool to read the data stream from the PCM. There are a few items a non-professional should check before taking the vehicle to a qualified technician for diagnosis and repair.



Check for a poor connection at the PCM or IAC motor. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connection. Inspect for a damaged wiring harness, especially if heavy work has recently been performed (intake manifold removal, engine removal, etc.) where the throttle body has been disturbed. Inspect for a restricted air intake system. Check for a possible collapsed air intake duct, restricted air filter element or foreign objects blocking the air intake system. Inspect the throttle body. Check for objects blocking the IAC passage or throttle bore. Excessive deposits, especially on high-mileage engines, can build up in the IAC passage and on the IAC pintle. Excessive deposits can also build up on the throttle plate, so check for a sticking throttle plate. Check for vacuum leaks such as disconnected hoses, leaks at the EGR valve and EGR pipe to the intake manifold, leaks at the throttle body, faulty or incorrectly installed PCV valve, leaks at the intake manifold brake booster hose connection, etc.



REMOVAL & INSTALLATION



  1. Disconnect the negative battery cable.
  2. Detach the electrical connector from the IAC valve.
  3. Remove the 2 attaching screws and remove the IAC valve from the engine. Remove the O-ring from the housing.

To install:



0900c15280217cd3.jpg enlarge_icon.gifenlarge_tooltip.gif

Fig. The Idle Air Control (IAC) valve is mounted on the throttle body-3.8L (VIN K) engine shown, others similar


NOTE Before installing a new IAC valve, measure the distance that the valve is extended. The measurement should be made from the motor housing to the end of the valve cone (pintle). The distance should be no greater than 1 1 / 8 inch (28mm). If the pintle is extended too far, adjustment is required, otherwise damage may occur when the IAC valve is installed. Adjust the IAC valve by compressing the pintle to achieve the correct length.


  1. Use a new O-ring, install the IAC valve and tighten the retaining screws to 18 inch lbs. (2 Nm).
  2. Attach the electrical connector.
  3. Connect the negative battery cable.
  4. The PCM will reset the IAC valve the next time the ignition switch is turned ON and then OFF .
  5. Start the engine and allow to warm to operating temperature to check idle quality.

Oct 13, 2010 | 2000 Pontiac Grand Prix

1 Answer

Engine stalls after it has been raining heavy. p0508 code then next day it runs fine


P0508 Idle Air Control Circuit Low.
This means that the Idle Air Control Circuit input is below acceptable limits.
You need to test the Idle Air Control (IAC) valve, the wiring between the IAC and the PCM and made sure the IAC passages in the throttle body are clean.

Your PCM unit may actually be faulty and letting moisture in

Sep 08, 2009 | 2004 Dodge Ram 1500

2 Answers

What is the function of the idle speed control valve?


The idle air control (IAC) valve assembly on a combustible engine monitors and manipulates the amount of controlled air moving around the throttle plate. The IAC valve is managed by the electronic control module (ECM) of the engine, which calculates the position of the IAC valve. Voltage pulses called counts extend and retract an internal conical-tipped shaft called a pintle inside the IAC valve. When the pintle is extended, the cone-shaped tip positions itself closer to the air inlet and restricts the amount of air allowed to pass through the throttle, building up more air around the throttle plate to increase the rpms of the engine. When the pintle is retracted, it moves away from the inlet and allows more air into the throttle away from the throttle plate, decreasing the rpms. The IAC valve operates and adjusts constantly while the engine is running to help prevent the engine from stalling or surging. This will not cause the engine to misfire!! Hopefully this helps

Aug 21, 2009 | 2002 Lincoln LS

1 Answer

Wiring diagram for 1993 toyota camery v6


Does the engine run properly when you drive it? Does it accelerate normally, or does it hesitate & ****? If it runs poor, it may be the wires crossed. If it just stalls at idle, you may have a bad Idle Air Control (IAC) valve, or a partially stuck open EGR valve.

Oct 01, 2008 | 1993 Toyota Camry V6

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