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How to adjust idle air control Does the ecm hold a memory of where the old motors position was after installing new one?

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  • Cars & Trucks Master
  • 11,737 Answers

There is no adjustment ,controlled by the computer !

Posted on Dec 20, 2016

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  • Jeff Armer Dec 21, 2016

    If the key isn't turned on and then disconnect the IAC valve , and replace it with new one , then connect it and turn key on it will idle where it's suppose to . No adjustment .

  • john soos Dec 22, 2016

    did that but the idle stayed at 1500 read an article by mitsubishi said to turn the ignition off and on 20 times that should reset it tried it worked 750 on they money can anyone tell me why.

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2 Answers

My 2000 new beetle dies when I turn the a/c on


I recommend you test the idle air control valve. See procedure below. If this is not the problem, please read additional possibilities at the link below.


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


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

Testing


Checking Idle Air Control Valve (IAC) Triggering
Check IAC valve is electrically OK.
Slide up boot on the IAC valve connector.
0900c152801c00a1-nx20irngy4ugyvyt2uth3oj4-3-0.gif

Fig. IAC Connector
Use scan tool 'Output Diagnostic Test Mode' function 03 to trigger the IAC valve - N71.Connect VAG 1527B voltage tester, or equivalent, between terminal 1 and engine ground (GND). Voltage tester must flash.Connect VAG 1527B voltage tester, or equivalent, between terminal 2 and battery positive voltage (B+). Voltage tester must light up.If specified results are not obtained:Connect VAG 1598/19 test box, or equivalent, to ECM harness connector.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 socketD9 using wiring diagram. Repair as necessary.If the wiring is okay, but triggering still does not occur, replace the ECM.If the triggering signal and the wiring are okay and the valve does not react, replace the IAC valve. Checking Mechanical Function
Remove the idle air control (IAC) valve.Visually check the surface of the rotary slide (arrow) for signs of wear.



0900c152801c00a2-nx20irngy4ugyvyt2uth3oj4-3-4.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.

Reconnect the IAC valve, while still removed, to the harness connector.Use scan tool 'Output Diagnostic Test Mode' function 03 to trigger IAC valve - N71.Check whether rotary slide moves freely from stop to stop.If there are signs of scoring, or if the rotary slide does not move freely in both directions, replace the IAC valve.If the IAC valve does not respond (not triggered) during the Output Diagnostic Test Mode, check triggering. Resistance Test
Remove the idle air control valve harness connector.Use a suitable Digital Multimeter (DMM) to measure the resistance between the 2 terminals of the idle air control valve.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.

Reconnect the idle air control valve harness connector.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.

Do It Yourself Diagnosis and Repair

Aug 03, 2017 | Cars & Trucks

1 Answer

Just replaced my idel air controle moter and it already broke


Hello. I believe there is a process for setting the pintle length on the idle air control motor...you need to look at a shop manual and it will detail how to measure the stickout of the old iac. Then you turn/ adjust/ unscrew the iac pintle. The pintle is the part that sticks out to regulate the idle by opening or closing/blocking the idle air port. If you do not adjust the stickout, the pintle is either out too far or too short, and then the motor cannot effectively regulate the idle. It burns the motor because the computer(ECU/ECM) keeps telling the motor to open or close the port MORE but it's at the end of the travel and burns up due to running constantly. Hope this helps...Good Luck, Brian

Apr 25, 2014 | 1996 Dodge Ram 1500 Club Cab

1 Answer

Hi, my rpm stays on high after cleaning the idle control valve


An IAC (idle air control) motor is designed to adjust the engine idle RPM speed by opening and closing an air bypass passage inside the throttle body. The cars computer or ECM (electronic control module) receives information from various sensors and will output signals to adjust the IAC motor in or out to adjust engine idle speed by controlling engine idle air. ----------------------------------------------------------------------------------------
XPROG-M V5.0

Feb 26, 2013 | Cars & Trucks

2 Answers

Stalls while in drive with foot on brake , changed MAP Sensor, Crank Shaft Sensor , Distributor, Fuel Pump, Fuel Filter , have ran out of ideas


I would check the IAC motor or idle air control motor, heres a little info.about the part.Stratus Sedan, 1999-2005 Idle Air Control Motor

Print


Description & Operation

Not for Dodge Stratus Sedan
The idle air control motor (IAC) attaches to the throttle body. It is an electric stepper motor. The PCM adjusts engine idle speed through the idle air control motor to compensate for engine load, coolant temperature or barometric pressure changes. The throttle body has an air bypass passage that provides air for the engine during closed throttle idle. The idle air control motor pintle protrudes into the air bypass passage and regulates airflow through it.
The PCM adjusts engine idle speed by moving the IAC motor pintle in and out of the bypass passage. The adjustments are based on inputs the PCM receives. The inputs are from the throttle position sensor, crankshaft position sensor, coolant temperature sensor, MAP sensor, vehicle speed sensor and various switch operations (brake, park/neutral, air conditioning).

0996b43f8020234f.jpg enlarge_icon.gifenlarge_tooltip.gif

Fig.

Not for Dodge Stratus Sedan
When engine rpm is above idle speed, the IAC is used for the following functions:


Off-idle dashpot 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)
The idle air control motor (IAC) attaches to the throttle body. It is an electric stepper motor. The PCM adjusts engine idle speed through the idle air control motor to compensate for engine load, coolant temperature or barometric pressure changes. The throttle body has an air bypass passage that provides air for the engine during closed throttle idle. The idle air control motor pintle protrudes into the air bypass passage and regulates airflow through it.
The PCM adjusts engine idle speed by moving the IAC motor pintle in and out of the bypass passage. The adjustments are based on inputs the PCM receives. The inputs are from the throttle position sensor, crankshaft position sensor, coolant temperature sensor, MAP sensor, vehicle speed sensor and various switch operations (brake, park/neutral, air conditioning).

21180_cdia_g257.jpg enlarge_icon.gifenlarge_tooltip.gif

Fig.

When engine rpm is above idle speed, the IAC is used for the following functions:


Off-idle dashpot 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)
Target Idle
Target idle is determined by the following inputs:


Gear position ECT Sensor Battery voltage Ambient/Battery Temperature Sensor VSS TPS MAP Sensor
Target idle is determined by the following inputs:


Gear position ECT Sensor Battery voltage Ambient/Battery Temperature Sensor VSS TPS MAP Sensor


Removal & Installation

  1. Disconnect the negative battery cable.
  2. Disconnect the IAC electrical connector.
  3. Remove the IAC mounting screws.
  4. Remove the IAC.

To Install:
  1. Install the IAC to the throttle body.
  2. Tighten mounting screws to 5.1 Nm (45 inch lbs.) torque.
  3. Attach electrical connector to the IAC.
  4. Connect the negative battery cable.

    0996b43f80202350.jpg enlarge_icon.gifenlarge_tooltip.gif

    Fig.


  1. Disconnect the negative battery cable.
  2. Disconnect the IAC electrical connector.
  3. Remove the IAC mounting screws.
  4. Remove the IAC.

To Install:
  1. Install the IAC to the throttle body.
  2. Tighten mounting screws to 5.1 Nm (45 inch lbs.) torque.
  3. Attach electrical connector to the IAC.
  4. Connect the negative battery cable.

May 11, 2012 | 2000 Chrysler Cirrus

1 Answer

I have a 1996 Eclips 2litre when you get in and start it with your foot on fuel it works fine when you take your foot off it dies out.Also its only getting 5amp/volts witch ever it is to the fuel ,map...


I am not saying 100% this is your problem because this is a fairly expensive part however your symptoms are classic IAC failure. An IAC (idle air control) motor is designed to adjust the engine idle RPM speed by opening and closing an air bypass passage inside the throttle body. The cars computer or PCM (powertrain control module) receives information from various sensors and will output signals to adjust the idle air control motor in or out to adjust engine idle speed by controlling engine idle air. An idle air control motor can fail one of two ways, either the motor short circuits and stops working or the motor will develop high resistance and cause the idle air control motor to react slowly, either failure can cause the engine to stall at idle. When a trouble code scan is performed it sometimes won't always detect a failed or weak idle air control motor. To check the idle air control motor remove the unit, with the wires connected turn the key to the "on" position without starting the engine, the idle air control should move in or out. If the idle air control motor does nothing it has probably failed, replace it with a new unit and recheck system. Note: while the idle air control motor is removed clean (use aerosol carburetor cleaner) the passages the idle air control uses to control idle air speed, also inspect the idle air control for a build-up on the seating (pointed) end and clean as necessary.

Jul 20, 2011 | Mitsubishi Eclipse Cars & Trucks

1 Answer

Just started idling rough, sometimes stalling


Shot in the dark here without knowing the vehicle but it could be an Idle Air Control valve starting to fail. An IAC (idle air control) motor is designed to adjust the engine idle RPM speed by opening and closing an air bypass passage inside the throttle body. The cars computer or PCM (powertrain control module) receives information from various sensors and will output signals to adjust the idle air control motor in or out to adjust engine idle speed by controlling engine idle air. An idle air control motor can fail one of two ways, either the motor short circuits and stops working or the motor will develop high resistance and cause the idle air control motor to react slowly, either failure can cause the engine to stall at idle. When a trouble code scan is performed it sometimes won't always detect a failed or weak idle air control motor. To check the idle air control motor remove the unit, with the wires connected turn the key to the "on" position without starting the engine, the idle air control should move in or out. If the idle air control motor does nothing it has probably failed, replace it with a new unit and recheck system. Note: while the idle air control motor is removed clean (use aerosol carburetor cleaner) the passages the idle air control uses to control idle air speed, also inspect the idle air control for a build-up on the seating (pointed) end and clean as necessary.

Jul 20, 2011 | Mazda B2300 Cars & Trucks

2 Answers

What is the stepper motor


It's called the Idle Air Control motor (IAC). It is on the side of the throttle body. This controls the idle speed. What it does is let in a certain amount of air into the engine, in steps. The more it is open the higher the idle speed. The ECM controls it.

May 17, 2011 | 1996 BMW 318

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

2 Answers

Idle fluxuates up and down consistantly


Check the Idle Control System

Idle speed is controlled by the Idle Air Control Valve (IACV). The IACV changes the amount of air being bypassed to the intake manifold, in response to electric current controlled by the ECM. When the IACV is activated, the valve opens to maintain proper idle speed.

Symptom and Subsystems to Check:

1. Difficult to start engine, when cold--check Fast Idle Thermo Valve.

2. Fast idle out of spec, when cold:
a. Check Fast Idle Thermo Valve.
b. Check IACV.
c. Check idle adjusting screw (see Section C).

3. Rough idle:
a. Check hoses and connections.
b. Check IACV.

4. RPM too high, when warm:
a. Check IACV.
b. Check Fast Idle Thermo Valve.
c. Check hoses and connections, check Power Steering Pressure Switch Signal, and check idle adjusting screw.

5. RPM too low, when warm:
a. Idle speed is below specified rpm, with no load--check IACV and idle adjusting screw.
b. Idle speed doesn't increase after initial start up--check IACV.
c. Idle speed drops in gear (automatic transmission)--check automatic transaxle gear position switch signal.
d. Idle speed drops when AC is on--check air conditioning signal and IACV.
e. Idle speed drops when steering wheel is turned--check power steering pressure switch signal and IACV.
f. Idle speed fluctuates with electrical load--check hoses and connections, IACV, and Alternator FR Signal.

6. Frequent stalling, while warming up--check IACV and idle adjusting screw.

7. Frequent stalling, after warming up--check idle adjusting screw and IACV.

Additional Steps:

. Check Alternator FR Signal. Have alternator inspected, if idle speed fluctuates with electrical load. The FR signal communicates to the ECM how "hard" the alternator is working to meet the electrical demands of the car, including the battery and any loads which aren't monitored by the ELD. This square-wave signal varies in pulse width, according to the load on the alternator. The ECM places, approximately, 5 reference volts on the wire. The voltage regulator will drop this signal to approximately 1.2 volts, in proportion to alternator load. The ECM compares the electrical load (ELD) signal with the FR (Charging Rate) signal from the alternator and uses that information to set the idle speed and turn the alternator on and off. This helps fuel economy.

. Clean main ECM ground on thermostat housing.

. Reset ECM, by removing the 7.5 amp Back Up Fuse, in the under-hood fuse box, for 10 seconds.

. Replace PCV Valve, cleaning hose with brake cleaner spray.

. Substitute a known-good ECM. If symptom goes away, replace original ECM.

Check the ICM (Erratic RPM and PGM-FI System)

When the engine is cold, the air conditioner compressor is on, the transmission is in gear (automatic transmission only) or the alternator is charging, the ECM controls current to the Idle Air Control (IAC) Valve to maintain correct idle speed. Here's an overview of how the PGM-FI System works.

Background:

Various inputs to the ECM are TDC/CKP/CYP Sensor, MAP Sensor, ECT Sensor, IAT Sensor, TP Sensor, HO2S, VSS, BARO Sensor, EGR Valve Lift Sensor, Starter Signal, Alternator FR Signal, Air Conditioning Signal, Automatic Transmission Shift Position Signal, Battery Voltage (Ignition 1) Brake Switch Signal, PSP Switch Signal, ELD, and VTEC Pressure Switch.

Inputs are received and processed by the ECM's Fuel Injector Timing and Duration, Electronic Idle Control, Other Control Functions, Ignition Timing Control, and ECM Back-up Functions. These are the primary functional areas within the ECM.

Outputs from the ECM control Fuel Injectors, PGM-FI Main Relay (Fuel Pump), MIL (Check Engine Light), Idle Air Control (IAC) Valve, A/C Compressor Clutch Relay, Ignition Control Module (ICM), EVAP Purge Control Solenoid Valve, HO2S Heater, EGR Control Solenoid Valve, Alternator, Lock-up Solenoid Valve A/B (A/T), VTEC Solenoid Valve, and Interlock Control Unit.

Idle RPM:

Once you understand how the PGM-FI system is configured, it's easy to see how the ECM, Idle Air Control Valve, and the Ignition Control Module affect idle rpm. If the ECM's Electronic Idle Control function is not working properly, then it cannot properly control the IAC Valve. Likewise, if the ECM's Ignition Timing Control function is not operating properly, it cannot properly control the ICM (igniter). Obviously, idle rpm will also be affected if there's a problem with the IAC Valve or the ICM. As stated above, the ECM controls current to the Idle Air Control (IAC) Valve to maintain correct idle speed. This cannot happen if the IAC Valve is failing. The same situation exists if the ICM is failing. The ECM will tell the ICM to open and close the primary voltage circuit going to the coil and it won't respond properly. The result will be erratic spark plug firing and erratic rpm.

Conclusion:

If you are experiencing erratic idle rpm, try and isolate whether the problem is caused by the ICM (ignitor), IAC Valve, or the ECM. My experience has been that a failing ICM is usually responsible for the problem. Keep in mind that tachometers are connected directly to the ICM. Therefore, a fluctuating tachometer needle is often a dead giveaway. Heat and poor preventive maintenance (causing high secondary voltage to be discharge on internal distributor components) frequently causes the ICM (and coil) to fail. Besides performance, this is another reason why it's important to regularly replace spark plugs, spark plug wires, rotors, and distributor caps. Electricity will always follow the path of least resistance, even if it isn't the intended one. Our job is to ensure the intended path is the path of least resistance.

Ignitor (ICM) and Coil Replacement:

1. Disconnect negative battery cable.
2. Remove hex head machine screws, securing distributor cap to housing, using an 8 mm nut driver.
3. Move distributor cap and wires off to the side.
4. Remove machine screw securing rotor to shaft, using a #2 Phillips head screwdriver. It may be necessary to "hit" the starter once or twice, in order to rotate rotor for access to mounting screw.
5. Remove rotor and leak cover.
6. Unfasten ignitor wires, remove coil mounting screws, and set coil aside. Note: Removing coil first improves access to igniter.
7. Unfasten screws securing igniter to housing.
8. Remove ignitor from distributor and unfasten screws mounting ignitor to heat sink.
9. Coat back of new ignitor (or old igniter, if reusing) and male connectors with silicone grease. Silicone grease increases heat transfer to heat sink. Failure to apply silicone grease will cause the ignitor to quickly fail.
10. Mount ignitor to heat sink and reinstall ignitor, igniter terminal wires, coil, coil wires, leak cover, rotor, and distributor cap. Ensure female ignitor terminals fit snugly--crimp with pliers, if necessary.

AutoZone can test ICMs and coils for free. If you plan to keep the car, I would replace the ICM due the age of your Civic.

Sep 15, 2010 | 1991 Honda Civic

1 Answer

Idle is too low, car dies, engine runs fine


An IAC (idle air control) motor is designed to adjust the engine idle RPM speed by opening and closing an air bypass passage inside the throttle body. The car computer or ECM (electronic control module) receives information from various sensors and will output signals to adjust the IAC motor in or out to adjust engine idle speed by controlling engine idle air.
An IAC motor is highly susceptible to carbon and coking build up; if an IAC goes too long without cleaning it can cause stalling and poor idle quality. Some cars are designed with a large vacuum transfer hose that connects the intake manifold to the IAC (idle air control) motor. If a broken or dilapidated these vacuum lines can cause the engine to lose vacuum which will allow the engine to run rough and die. 
Inspect all engine and accessory vacuum lines to look for missing, torn or dilapidated lines and replace as needed. To check the IAC motor remove the unit, with the wires connected turn the key to the "on" position without starting the engine, the IAC should move in or out. 
If the IAC motor does nothing it has probably failed, replace it with a new unit and recheck system. Note: while the IAC motor is removed clean (use aerosol carburetor cleaner) the passages the IAC uses to control idle air speed.

Good luck and hope this helps

May 08, 2009 | Honda CR-V Cars & Trucks

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