Question about 2003 Toyota Highlander

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ENGINE IDLE I have the 3.0L V6. I'm having an idle problem when the air conditioner or defrost is being used. When I'm at a stop light, the engine will sound like it's hesitating about every 30 seconds as the compressor kicks in. However, I have noticed that it does the same thing when the AC isn't on, just not as severe. It's as if the engine isn't holding a constant, smooth idle.

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  • bhtto Oct 30, 2008

    I suppose I should say that the engine seems to want to stall particularly when the AC is on. I do know that the compressor runs during defrost.
    For instance, when I pull up to a light, the engine will idle down fine, but then it will go to a brief, rough, almost stalling idle, and then go back to normal. I have noticed this more (and it is stronger) when the AC compressor is activated.
    However, I have noticed that it occurs during times of not having the AC compressor on...it's almost as if the engine is cycling from an extremely low, rough idle, to normal idle. It's not as strong with the AC off, but it is certainly there. It seems to be aggravated more by the AC. This is a relatively new problem...within the last six months.


  • bhtto Oct 30, 2008

    Thanks a lot Toyota Ed. No, the Check Engine is not on. The car has 86,000 miles on it, so I suppose it could need new plugs too, although Toyota says not. I'll get the induction done first, and let you know what happens. Again, thank you.

  • Anonymous Feb 17, 2009

    I have a 2001 Highlander, with a similar problem. I have replaced the plugs, va.,ve cover gaskets, and this weekend the Idle Air Controller valve. Still have the problem. I have noticed that idle gets worse as engine gets warmer. Wasted $300+ on the part and fluids. I did this after a dealer said it had to be the IAC. It is really annoying to have the idle drop 100 or so RPMs and stumble, then jum back to normal idle.

  • Toyota Ed May 11, 2010

    Get the induction done, and then replace the plugs. Don't replace the plugs before the induction. The cleaner may foul the new plugs. And, please use Toyota plugs, don't use "aftermarket" plugs, they do not work well in the 3.0's

  • Toyota Ed May 11, 2010

    I assume that the check engine light is not on...yes?

    IF not, I would start to look after the induction system, assuming that the engine is in a proper state of tune (ne plugs/air filter, etc.) Mayhap an induction cleaning would be in order, as the idle is controlled by the admittance of additional air to the intake to achieve a specific idle speed. Also, a sticking EGR valve could add to this issue, but, the most common thing that I see is the Idle Air Control (IAC) valve not responding quick enough.

    What I would do: Get an induction cleaning done, and, if there is no improvement, replace the IAC. Advise of any improvement, either way. Hope this helps.

  • Toyota Ed May 11, 2010

    Please provide more info regarding the idle, with all of the heater/AC controls OFF.

    Please note that the AC compresser DOES run when you have the defroster ON.

    This is a normal condition.

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5 Suggested Answers

  • 1861 Answers

SOURCE: Engine knock

The idle issue is normal. The idle is controlled by the ECU. There are no adjustments for the idle. Regarding the knocking noise, that could be several things, and I am hesitant to comment without hearing it. Take it to a Toyota Dealer & have a tech listen to it. We are very good at identifying noises on the service drive.

Posted on Sep 09, 2008

Molson02536
  • 3854 Answers

SOURCE: 1995 z-28. air conditioner compressor won't kick

Your A/C pressure switch may have gone bad or the wire harness to it may have gone bad. The switch is along the low pressure line or on the A/C Accumulator ( looks like a silver canister) , Unplug the wire and you can jump it there and see if the clutch comes on, if it does try spreading the two tabs apart on the switch and clipping the wire back on. If it does not come back on you need to replace the switch, you can do it with out loosing to much R134A. Just got to be quick when you  remove the old one and placing the new one. The low side should have a reading of 30PSI to 50PSI and the high side should have 150PSI to 200PSI. Any other reading will give you poor A/C performance. Good luck and hope this helps.

Posted on Jun 23, 2009

  • 94 Answers

SOURCE: Air conditioner doesn't run.

If your AC compressor is cycling constantly this is a sign of a low refrigerant level. The system will need to be inspected for any leaks, any leaks repaired, and the system charged to the proper level with refrigerant.

Posted on Jul 08, 2009

  • 62 Answers

SOURCE: 1994 Toyota pickup 22re 4cyl has intermitent low,

You might have a bad coil. Under a load the coil might preform well, but under no load, its weak causing a misfire...thus giving you a rough idle. I have had this problem on a few vehicle. Check plugs, wires, and distributor. Mike.

Posted on Sep 18, 2009

SOURCE: 2001 toyota echo engine light is on. Car idle is rough and sometimes stalls. Is there a way to clean the idle air control valve without removing it?

Yes, I just had the same problem and I cleaned it with STP throttle body and carb cleaner. Take off the air big air hose off of the throttle body. You will see a small hole on the lower right side. Put the spray nasal on your cleaner can. Stick the plastic nasal directly into the hold and spray it for about 7 seconds. Then take the nasal off of the can and stick it in the hole pushing it in and out for a few minutes. Then put nasal back on the can and spray for another 7 seconds. Now wait for 20 minutes. spray one last time for a few seconds and you are good to go. You will be shocked on how much better you echo will run. I almost spent 225.00 for a new idle control valve, man I sure am glad I did this. My car is running better now then when I first bought it. Good Luck !!

Posted on Apr 26, 2013

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you stated you had codes p0171 and p0174 these are lean codes for bank one and two, you said you found a vacuum leak and repaired it, the vacuum leak was mostly likely the cause of the lean codes, however the pcm has calibrated the fueling stategy for this lean mixture, what you need to do is erase the KAM "keep alive memory" this is done by unhooking the negative battery cable for 60 seconds, this is the only way to erase the KAM the $6000.00 machine I use wont even do it.

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NGEC0549
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NGEC0549S01
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I Battery
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SEF976U
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SEF977U
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SEF217U
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SEF975R
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GI
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PD
AX
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BT
HA
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