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Idle drops way low with fan,lights,ect..., on@ operating temp195, IAC is good power,no leak, power from computor;yes,under load, lights ect..,what am I overlooking? 91GeoMetro 3 banger

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  • Cars & Trucks Master
  • 786 Answers

The electrical load on the alternator will pull the engine RPM down. It takes 10 H.P. to run the alternator. The only recourse to low RPM at idle would be to install a larger diameter pulley on the alternator. Extended idle could result in low battery charge rate. Should be fine at hi way speed. The alternator will not put out below 750 Rpm.

Posted on May 20, 2017

  • Tim Morey
    Tim Morey May 20, 2017

    Should'nt the idle speed control compensate for that drop in rpms?

  • Joe Stanton May 20, 2017

    Not with everything electrical switched on. This car probably only has a 60 amp alternator. Full fielding applies dynamic braking to the engine

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Where is the air control sensor in a 2001 oldsmobile silhouette?


It's called IAC - idle air control valve > Did the RPM'S stay at 2000 or drop back down ? The PCM engine computer controls IAC valve according to engine load . Put it in gear , turn on electrical loads , headlamps , A/C etc... an the RPM raise's up so engine will not stall . More then likely the throttle plate needs to be cleaned , they get gummed up an stick at higher idle . Quick Tip Throttle Cleaning EricTheCarGuy If the IAC valve were gummed up the idle would be low or erratic . On some engines a vacuum leak will cause high idle . Videos on youtube checking for vacuum leaks .

Jul 24, 2016 | 2001 Oldsmobile Silhouette

2 Answers

What is an IAC Valve


Google is your friend in such questions.

  • Idle air control actuator - Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Idle_air_control_actuator An idle air control actuator or idle air control valve (IAC actuator/valve) ... Idle air control actuator; MAP sensor; Mass flow sensor; Oxygen sensor; Starter motor;
  • how to tell if your iac valve is going bad - YouTube www.youtube.com/watch?v=oNO8GCN8jQA
    • BY TIMMY102345
    • 6 MIN
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    2009-09-07 · Video embedded · how to tell if your iac valve is going bad timmy102345. ... #372 Better repair method Toyota Camry Idle Air Control Valve - ...
  • 4 Ways to Check an Idle Air Control Valve - wikiHow www.wikihow.com/Check-an-Idle-Air-Control-Valve
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    2015-12-11 · How to Check an Idle Air Control Valve. ... Again, an idle air control valve can have an issue or fault without triggering a check engine light. 2.


  • There are also videos in this link. How to check and fix.

  • What is an IAC Valve Bing video

    May 12, 2016 | 1992 Toyota Paseo

    1 Answer

    2003 Ford Explorer XLT Wants To Stall At Low Idle,, especially when at a stop light


    How does it idle in park , does it run ruff or smooth? Are any lights lit on the dash , check engine etc. ? Could have a partially plugged IAC air passage .idle air control (IAC) valve ! The engine computer uses the IAC to control idle , when under a load such as when put into gear the computer raises the idle ! It does this by allowing more air to by pass the closed throttle into the engine raising the idle ! If these air passages clog they restrict the air flow an cause a idle problem ! Now if it runs ruff at idle in park you could have vacuum leak ! Rough Idle How to Fix Ford Taurus Engine Stalls at Stop Signs

    Mar 19, 2015 | 2003 Ford Explorer

    1 Answer

    My car starts fine when engine is warm. I turn it off then try starting it again. then starts up and shuts back off. does it like 3 times in a row. then I wait a few minutes then it starts up when I push...


    stalls, are complex
    if the engine is good (compression at spec)
    it this list.
    1: lost electric power to EFI system or spark.
    2: bad fuel.
    3: bad spark.
    4: bad fueling. (too much or too little.
    5: EGR stuck open
    6: ISC dead. or IAC dead. (idle air valves failing cold)

    there are tests for each.
    cold start failure only ! all else good, engine tuneup done?
    1: ECT fibbing like oh'bummer. (signals water temps of alaska in Panama? "floods, and your right foot helps./..........
    2: IAC (cold start fast idle air valve bad) same for right foot....
    3: check engine light on running? is it?

    ECT can cause gross over fueling.
    the IAC dead will cause gross under AIR which in fact causes flooding (less air plus same fuel = flood)
    bad fuel.


    Oct 12, 2013 | 1999 Honda Accord

    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

    3 Answers

    Rough Idle when cold runs seems to run ok hot but still almost stalls when you turn on AC and you are at a stop also noticed that the volt meter reads 9v with the AC and the lights on with the AC and...


    mcdevito75 here, Sounds like a faulty voltage regulator, it"s 1 unit with the alternator, change the alternator, also the alt. supplies juice to the ignition switch, distributor abd plugs, thus a rough idle due to bad alternator.

    Jun 19, 2010 | 1994 GMC Suburban

    1 Answer

    Engine Light On


    If you notice idle getting too low, or car stalling on turns, or when AC /heater is on etc, (engine under load) then yes, probably IAC motor is defective, or dirt in the seat area of it. Only thing to be aware of, is it might stall when off the gas, so be careful when turning, and/or stopping. Have it looked at first chance, but it shouldn't hurt vehicle, just be cautious driving when you let off the gas, it could stall.

    Nov 19, 2009 | 2005 Dodge Stratus

    1 Answer

    Engine Miss on 96 camaro possibly Ignition related?


    yes coil or the power washer blew a vacuum line apart..check for vacuum leaks good luck

    Nov 22, 2008 | 1998 Mitsubishi Galant

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