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2001 Toyota Highlander Question: Idle problem again worse

 

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montuno, 3.0L V6, San Juan, PR, September 17, 2009, 22:17
 Rookie

Hi...I know this is a common problem with the idle control valve, the first time the cleaning trick did the job and lasted for around a year and a half but never removed the part to clean very good. So the problem started happening again and this time decided to take the throttle body off to take the complete valve off and clean good(now turns really smooth), since I had the body off I also lightly cleaned it but never soaked it or heavely sprayed it I know there are other sensors in it. Reassemble the whole thing and when started it was worse than before...at least before it would run with low RMPS and fix it self after a while, but now it just wont run unless I keep the pedal down and it dies if I remove it. I thought that this time the valve motor died for good so I took my sisters lexus rx that has the same part but did the same so its not the iddle control valve, thought I damaged the electrical plug removing it but the valve turns when the ignitions is in the on position. Tried her MAF sensor nothing, I am leaning towards the throttle position sensor now ...maybe got damaged when I took the body off ??? Is this what the engine does if the TPS is bad ???. Since my sister wont let me take her TPS to try on mine cuz I have to remove the throttle body I took it to a mechanic after 3 days,he said it was the computer bad LOL...I have a friend that works at a computer repair shop and he cheked it and said is good(I knew that!) he sended me to another mechanic after a couple of days he said that the throttle body is bad!!!! ???? because he tried another body on it and started working fine but he did not tried individual sensors!!! What do you guys think ???

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    patrick mannion from Greg Solow's Engine Room, September 18, 2009, 07:28
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     Master

    This style of idle air control motor (IAC) does give problem, it is not necessary to remove the entire throttle body to clean it. I remove the air induction boot, and at the bottom of the throttle butterfly housing is the IAC motor. On the Toyota/Lexus IAC of this design, I remove the two philips screws holding the plastic coated armature of the IAC motor, this exposes a small shaft approx 8mm in diameter. take this between your fingers and rotate it forward and backward it should rotate freely and not bind! If it does bind, clean the throttle butterfly and butterfly housing with a soft tooth brush and "Chemtool" or similar product. as you spray Chemtool into the throttle housing allow Chemtool to enter the air by pass passageway and rotate the IAC spindle back and forth spraying a little more Chemtool into the bypass passageway. When it moves freely reassemble the two philips screws and IAC housing. After assembly many professional quality scan tools have the capability of driving the IAC motor up ward and downward to test it. At this stage you can confirm you have" fixed" the problem or need to replace the valve. It is important not get Chemtool into the throttle position Switch (TPS) as it will harm it.
    I suspect you have a vacuum leak problem of some sort, probably the throttle housing gasket or perhaps a vacuum hose got misplaced.
    Many automotive repair shops have a machine that generates an inert non flammable low pressure smoke that looks similar to cigar smoke. The intake manifold is sealed off, and smoke is put into the engines intake manifold. The smoke then fills the engines crankcase and if there are any vacuum leaks from gaskets, hoses, or housing smoke emits from the source of the leak. Some mechanics will use propane or aerosol carburetor cleaner, with the engine running they will spray the cleaner or propane around the intake manifold and vacuum hoses. A leak will cause a "lean mixture" condition, when the flammable fuel (carburetor cleaner or propane) comes in contact with the source of the vacuum leak the engine idle speed will raise as the engine has received "fuel". this method of finding a vacuum leak works but is not recommended as it can easily cause a fire. TPS failure won't cause the engine to stall. Air flow meter problems will cause stalling and a check engine light to come on if it experiences a problem.
    I would check for vacuum leaks, and then plug in a scan tool to monitor sensors inputs and outputs rather than have to do intrusive testing you can read sensor values right of the scan tool and also scan to see if you have a fault or pending fault seen by the computer in your car.
    If you have a problem with the computer in your car send it to Fuel Injection Corporation, 2407 Research Drive,Livermore, CA 94550, Phone: 925-371-6551 they will test or repair it, great service quick return time, and inexpensive.

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    patrick mannion, September 18, 2009, 08:15
    Profile_thumbnail
     Master

    This style of idle air control motor (IAC) does give problem, it is not necessary to remove the entire throttle body to clean it. I remove the air induction boot, and at the bottom of the throttle butterfly housing is the IAC motor. On the Toyota/Lexus IAC of this design, I remove the two philips screws holding the plastic coated armature of the IAC motor, this exposes a small shaft approx 8mm in diameter. take this between your fingers and rotate it forward and backward it should rotate freely and not bind! If it does bind, clean the throttle butterfly and butterfly housing with a soft tooth brush and "Chemtool" or similar product. as you spray Chemtool into the throttle housing allow Chemtool to enter the air by pass passageway and rotate the IAC spindle back and forth spraying a little more Chemtool into the bypass passageway. When it moves freely reassemble the two philips screws and IAC housing. After assembly many professional quality scan tools have the capability of driving the IAC motor up ward and downward to test it. At this stage you can confirm you have" fixed" the problem or need to replace the valve. It is important not get Chemtool into the throttle position Switch (TPS) as it will harm it.
    I suspect you have a vacuum leak problem of some sort, probably the throttle housing gasket or perhaps a vacuum hose got misplaced.
    Many automotive repair shops have a machine that generates an inert non flammable low pressure smoke that looks similar to cigar smoke. The intake manifold is sealed off, and smoke is put into the engines intake manifold. The smoke then fills the engines crankcase and if there are any vacuum leaks from gaskets, hoses, or housing smoke emits from the source of the leak. Some mechanics will use propane or aerosol carburetor cleaner, with the engine running they will spray the cleaner or propane around the intake manifold and vacuum hoses. A leak will cause a "lean mixture" condition, when the flammable fuel (carburetor cleaner or propane) comes in contact with the source of the vacuum leak the engine idle speed will raise as the engine has received "fuel". this method of finding a vacuum leak works but is not recommended as it can easily cause a fire. TPS failure won't cause the engine to stall. Air flow meter problems will cause stalling and a check engine light to come on if it experiences a problem.
    I would check for vacuum leaks, and then plug in a scan tool to monitor sensors inputs and outputs rather than have to do intrusive testing you can read sensor values right of the scan tool and also scan to see if you have a fault or pending fault seen by the computer in your car.
    If you have a problem with the computer in your car send it to Fuel Injection Corporation, 2407 Research Drive,Livermore, CA 94550, Phone: 925-371-6551 they will test or repair it, great service quick return time, and inexpensive.

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    patrick mannion, September 18, 2009, 08:15
    Profile_thumbnail
     Master

    This style of idle air control motor (IAC) does give problem, it is not necessary to remove the entire throttle body to clean it. I remove the air induction boot, and at the bottom of the throttle butterfly housing is the IAC motor. On the Toyota/Lexus IAC of this design, I remove the two philips screws holding the plastic coated armature of the IAC motor, this exposes a small shaft approx 8mm in diameter. take this between your fingers and rotate it forward and backward it should rotate freely and not bind! If it does bind, clean the throttle butterfly and butterfly housing with a soft tooth brush and "Chemtool" or similar product. as you spray Chemtool into the throttle housing allow Chemtool to enter the air by pass passageway and rotate the IAC spindle back and forth spraying a little more Chemtool into the bypass passageway. When it moves freely reassemble the two philips screws and IAC housing. After assembly many professional quality scan tools have the capability of driving the IAC motor up ward and downward to test it. At this stage you can confirm you have" fixed" the problem or need to replace the valve. It is important not get Chemtool into the throttle position Switch (TPS) as it will harm it.
    I suspect you have a vacuum leak problem of some sort, probably the throttle housing gasket or perhaps a vacuum hose got misplaced.
    Many automotive repair shops have a machine that generates an inert non flammable low pressure smoke that looks similar to cigar smoke. The intake manifold is sealed off, and smoke is put into the engines intake manifold. The smoke then fills the engines crankcase and if there are any vacuum leaks from gaskets, hoses, or housing smoke emits from the source of the leak. Some mechanics will use propane or aerosol carburetor cleaner, with the engine running they will spray the cleaner or propane around the intake manifold and vacuum hoses. A leak will cause a "lean mixture" condition, when the flammable fuel (carburetor cleaner or propane) comes in contact with the source of the vacuum leak the engine idle speed will raise as the engine has received "fuel". this method of finding a vacuum leak works but is not recommended as it can easily cause a fire. TPS failure won't cause the engine to stall. Air flow meter problems will cause stalling and a check engine light to come on if it experiences a problem.
    I would check for vacuum leaks, and then plug in a scan tool to monitor sensors inputs and outputs rather than have to do intrusive testing you can read sensor values right of the scan tool and also scan to see if you have a fault or pending fault seen by the computer in your car.
    If you have a problem with the computer in your car send it to Fuel Injection Corporation, 2407 Research Drive,Livermore, CA 94550, Phone: 925-371-6551 they will test or repair it, great service quick return time, and inexpensive.

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  • Answer #2

    Visitor, December 28, 2010, 10:26

    Because you replaced the IAC valve you may simply need to do an Idle re-learn proceedure. I will specify the proceedure below, but even more I believe if you are interested in DIY it may be good to go to a site where others (myself included) frequently pass on such knowledge. See Maxima.org or NissanClub.com.

    Idle Air Volume Learning Procedure
    1) Start engine and warm it up to normal operating temperature.
    2) Turn ignition switch OFF and wait at least 10 seconds.
    3) Confirm the accelerator pedal is fully released, turn ignition switch ON and wait 3 seconds.
    4) Repeat the following procedure quickly 5 times within 5 seconds.
    1) Fully depress the accelerator pedal.
    2) Fully release the accelerator pedal.
    5) Wait 7 seconds, fully depress the accelerator pedal and keep it for approx. 20 seconds until the MIL goes off.
    6) Fully release the accelerator pedal within 3 seconds after the MIL goes off.
    7) Start engine and let it idle.
    8) Wait 20 seconds.
    9) Rev up the engine two or three times and make sure that idle speed and ignition timing are within the specifications.

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