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  • 3.1L Rough Idle.

    Hey guyz, I have a cav with a 91 3.1L 5spd in it.

    Since I took my car out of winter storage, every time I come to a stop it starts idleing rough. (however it dosent do it when its still cold) What it does is once I stop it idles fine at bout 900RPM with bout 225psi oil pressure. (needle straight up) for about 10 seconds. Then, my RPMs drop to bout 750-800 and my oil pressure drops to bout 100psi (needle at the first tick) and the RPMs & oil psi bounces back and forth between 800 and 1000RPM. If i give it a lil bit of gas & hold the engine to about 1000RPM the oil psi is fine and it dosent rev.

    Over the winter I removed / unplugged all the A/C stuff. I dont know if may make a difference but I did. Also, I thought it might have been just bad gas, but im now on my 3rd tank (Sunoco Ultra94), and ive put over 1000km on it since I took it out. Ive also replaced the coils, ICM, wires & plugs. Ive also tried the idle relearn several times... After the processs itll idle fine, but as soon as I drive it and come to a first stop it revs again. Im really stump here, anyone have any other ideas?

    The First 3400 Powered J-body Sedan

  • #2
    Sounds like it could be the IAC valve. Also, when you take off from a stop, does it hesitate for like a half second then take off?
    Robby Whitesell
    2006 Pontiac G6 GT
    1985 Toyota Pickup DLX

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    • #3
      You do mean kpa for oil pressure, right? I can't imagine 225 PSI of pressure in there!


      Cliff Scott
      89 BerettaGT
      89 Volvo740
      Cliff Scott
      89 BerettaGT
      04 AleroGX

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      • #4
        Im not sure if it hesitates from a stop, I know it kinda bogs for a moment when i rev it tho. same dif? also yes, i meant kpa.

        The First 3400 Powered J-body Sedan

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