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2009 GX Rough Idle Issue

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  • 2009 GX Rough Idle Issue

    I have a 2009 GX with 130k miles on it. I have kept up on the maintenance. This last Spring/Summer I had the spark plugs replaced at the local CNG shop and had the transmission fluid serviced. Two weeks ago, I started to notice a rough idle when I was a red lights, it acts as if it is mis-firing every 30-45 seconds. Since, it has gotten worse, accelerating at low speeds it wants to lurch or have a loss of power, act like it is mis-firing. If I turn on the AC - it get much worse especially at idle. This is the first major issue with the car, which I bought in 2014 @ 7.5k miles. Once I get going, it runs like a dream.

    I replaced the PCV Valve and it might have gotten worse.

    We are in the middle of winter here in Utah and I do not run the AC. Also the check engine light does not light up, and I had the computer scanned and no codes popped up while it was doing this. I can't tell if it is the transmission or possibly the AC is turning on and off, even though it is not running (bad fan?). Any ideas?

  • #2
    Depending on how low the air temp outside is, the a/c compressor does operate, along with heat. It acts as a de humidifier on the windshield. on the defrost mode.. At extreme low temps the defrost only uses the heat. I know this does not explain rough running. just info.


    • #3
      Might need a valve adjustment.


      • #4
        I had pretty much the exact same issue with my '09 last winter, apart from the part about the AC. The misfires were always worst when backing out of a parking space and the engine would often die while doing so. Wound up needing to have the ignition coils replaced.


        • #5
          Just bought an 09.. it randomly, rarely but sometimes, idles bad.. fuel pressure doesn't drop below 29... and i'm doubting it's the spark plugs since it's not constant.. So i was thinking one of my ignition coils might be bad.

          also no codes. I have 100k miles on it.


          • #6
            I have a 2012 GX and had similar issues on cold mornings. I finally decided to adjust the valves in the engine and wow what a difference. No more issues at all. There are countless YouTube videos that will walk you through it. Took me two hours total.


            • #7
              Adjusting valves is much easier than the Honda service manual or any YouTube video shows of Honda valve adjustments. To adjust valves on ANY four stroke engine, use the "exhaust opening/intake closing method". Rotating the crankshaft in the normal direction, adjust the intake valves when the exhaust valves start to open. Adjust the exhaust valves when the intake valves are almost closed.