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Rpm dipping with a/c on

I have had the motor die when the car is idle and has the a/c on. The rpm dips down low every 1.5 seconds or so. Turning the a/c off immediately stops the rpm dipping, and puts it back at a constant level.

Posted by Anonymous on

  • 2 more comments 
  • Anonymous Apr 05, 2015

    This is a toyota solara 2002

  • Anonymous Apr 07, 2015

    Also, there is a clicking sound coming from the engine itself that correlates with the dips in rpm. A clerk at autozone told me it could be freon levels. The lights on the dash inside the vehicle also dim during the rpm dips.

  • David Harrelson
    David Harrelson Apr 07, 2015

    Not absolutely certain, but I think the ECU is supposed to increase rpms when the compressor is triggered, but it is possible your A/C system has a problem such that the compressor is adding an abnormal drag on the engine. This can happen when the system has too much freon, but more commonly this indicates the compressor is failing.

  • Anonymous May 16, 2015

    Problem was the idle air control. You have to take the plastic piece off that covers the knob, spray throttle body cleaner into the air intake, and twist the knob back and forth for several minutes to make sure it turns freely. On my vehicle, it was so gunked up the thing wasn't even turning.

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The AC draws power from the engine as the clutch is engaged on the compressor. The dip in the RPMs is the clutch engaging and disengaging when the RPM returns to normal.. it is normal to cycle like how you are stating, but at 1.5 seconds, you might have a mechanic test the freon charge because it sounds like it might be leaking either oil or gas. Normal is to cycle abour every couple of minutes not seconds..

Posted on Apr 10, 2015

Testimonial: "Yea, thanks Stan, I just fixed it today by buying a 30 dollar can of freon with a gauge on it. Somehow it was in the red and had way too much freon."

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  • Cars & Trucks Master
  • 5,316 Answers

Most engines have a device of some sort to bump up the idle speed when A/C is on. As you don't tell us what you are working on hard to say what yours has for this purpose.

Posted on Apr 07, 2015

  • Anonymous Apr 07, 2015

    I put the name of the vehicle in the box when i asked the question. I also put the name of the vehicle in a comment below it, along with additional information.

  • Anonymous Apr 07, 2015

    2 days ago.

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Couple of things to look into since you ruled out the Freon:1. Check your idle regulator in the compressor connections.. The reason is that most cars are programmed to disable the compressor when you are at a high acceleration (push gas pedal hard) so that you have the extra energy to go instead of pushing the compressor around while trying to get out of someone's way. If this is off, it can be confused in knowing if you are accelerating or not and mess with your idle like you are seeing..
2. Check the reed valve in your compressor: If your reed valve is bent open, you will see the same issue because of the fluid not vaporizing through the spray nozzle through the reed valve like it should.. it is simple to check: Is the air super cold in the car or just kind of so-so? Cold is good, and so-so is a blown reed valve. 3. Last check your AC clutch in that it is engaged all the time (watch where the wheel and belt meet to see if it is turning all the time with AC activated or if it is engaging and disengaging with the idle speed changes.. that should be easy to do too.. just look at the compressor wheel at the belt.. If that is not staying engaged all the time, it could be a clutch or coil overheating which drives the clutch.. Let me know how it is going! Also let me know what kind of car you are looking at..
STan

Posted on Apr 27, 2015

  • Anonymous Apr 27, 2015

    Thanks for the comprehensive answer, Stan. I googled 'idle regulator' for my vehicle (toyota camry solara 2002), and did not find anything that showed me where it was. The air blows cold for sure. The clutch does appear to engage/disengage coinciding with these dips, as there is a loud clicking sound coming from the motor area at the same time the idle goes down. It's also worth noting that usually it does this only while the car is in Drive or Reverse. From all of my experience with it, I seem to recall it stopping in one of two situations: putting the vehicle in Park, and hitting off on the a/c.

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yankstorm02
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SOURCE: my car idle dips to low RPM at a stop i give it gas it dies

Is the engine light on? Check the air inlet hose between the throttle body & MAF sensor for cracks or leaks. Try unplugging the MAF & see if there is any difference

Posted on Apr 17, 2009

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SOURCE: My 2004 PT Cruiser 4

You said you just had the spark plugs replaced, could be that a spark plug wire was connected in the wrong spot, I would check that first, also does the car run smoothly going down the road? clogged fuel filter perhaps. Check engine light on? could alse be a sensor. This newer vehicles basically use a computer to control every aspect of the engine as far as keeping it running at top performance and the least amount of emmissions as possible.

Posted on Sep 03, 2010

isaid
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SOURCE: when I take foot off

time for a tune up!

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SOURCE: my 06 mustang v6, idle

could be a egr valve blocked or faulty ?? needs put on computer......

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headstrong56
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SOURCE: have 95 camaro win it gets hot it runs on hwy fine but when you stop oil drops to 0 if you put in park idle up and down and dies take dip stick out and idle up

sounds like you may need a new oil pump

Posted on Jul 31, 2012

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