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Idle dropping way before 1 rpm when A/C is on (compressor)

Discussion in '7G Lancer and older- General Information' started by LancerProject, Jul 22, 2011.

  1. LancerProject

    LancerProject Member

    Whats up guys, thanks for the idle adjustment help on my other post. One small turn of the idle screw with the TB cleaner an I new air filter, now its tip top shape. With A/C off

    My question now is that when the A/C is on an only when I hear the compresser turn on, the idle will drop and the engine boggs for a few second. Compressor turns off, idle runs fine. Compressor turns on then the engine boggs for a few second again. This happens off on will in drive at a stop sign or light.

    This only happens with I have the car in R or D. In park it idles fine with A/C on and off. I cranked the idle up higher than 1 rpm ..like 1.5 an it still drops when that compressor turns on. Possible spark plug change? I havent popped them out to look at them yet.

    THanks again,
     
    LancerProject, Jul 22, 2011
    #1
  2. 1slowlance

    1slowlance Well-Known Member

    this happens to me, but all the time. My idle will be around 1.2k and with the a/c on in park, it'll drop down to about 500-600.
     
    1slowlance, Jul 23, 2011
    #2
  3. lancer2quick

    lancer2quick Well-Known Member

    Could be that the compressor is starting to seize, causing the engine to work harder to idle.....cause when my compressor kicks on, RPMs go from 850 to 1k
     
    lancer2quick, Jul 23, 2011
    #3
  4. 1slowlance

    1slowlance Well-Known Member

    I thought when the compressor comes on, the rpms should jump up, right?
     
    1slowlance, Jul 23, 2011
    #4
  5. LancerProject

    LancerProject Member

    Is there possibly a switch (like a relay switch) or something that kicks on and raises the idle when the A/C compressor kicks on? Cause I notice that when the compressor comes on, it drops my idle to very low RPM's.

    If so what is it called an where is it located? Thanks guys
     
    LancerProject, Aug 9, 2011
    #5
  6. Jogenmaru

    Jogenmaru Well-Known Member

    There is no relay. It's all programmed into the ecu. The belt connected to the ac condensor is always spinning in nuetral when the ac is off. Once you turn the ac on it then engages a gear in the ac condensor unit that puts more strain on the engine making it pull more. Your ecu then tells your engine to increase in rpms so there is no loss in power to the other mechanisms for the engine to attain enough power to move the car. If for some reason your idle drops and doesnt increase afterwards then there is either 1 of 2 things wrong. Your ecu is programmed wrong(which is highly unlikely even if you bought it used) or your condensor is going bad. Or the clutch in the condensor or rather the "pressure plate" in the clutch of the ac is going bad.

    If you understood how the clutch/pressure plate combo works then you would understand what needs to be fixed, but in most cases it is easier to replace the whole ac condensor rather than fix the clutch issue. This also happens when you run low on freon. Basically the pressure plate is applying tooo much pressure forcing the engine to overwork and thus you dont get your desired idle that the ecu is telling it to do. There are other factors in this such as your alternator or battery going bad as well. But the most likely cause is running low on freon or ac condensor going bad.

    Take it too someone who specializes in auto a/c units and he can tell you exactly whats wrong. For a price but you know what exactly to fix instead of replacing the whole system.

    So overall...with a normal working ac unit in your car...your rpms should drop then jump up a little above normal idle. If your unit is having issues then it will cause the car just to see the drop in idle.
     
    Jogenmaru, Aug 9, 2011
    #6