Running Rich, Code 31

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Thread: Running Rich, Code 31

  1. #1
    Great White mysupratoy94's Avatar
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    Running Rich, Code 31

    Hey guys, so a while back my 93.5 NA was stalling after a few seconds. We determined it was an ECU issue because I was not getting my CEL with key in ignition and my scanner would not communicate with my ECU. I had some leaking resistors so I had the ECU repaired.

    I went ahead and installed it and now the car stays on, I get my CEL and so on but it was idling very low and got a CEL 31 code.

    While I was checking for vacuum leaks I checked my spark plug wires and noticed some arching. Wires were bad. I went ahead and replaced plugs, cap and rotor, wires, valve cover gaskets, PCV valve, EGR and Throttle Body gaskets and cleaned both EGR and Throttle body. Also cleaned the IAC valve.

    Now I can actually drive the car without it stalling but its running super rich and I'm still getting code31. I went ahead and removed the air flow sensor since that's what code 31 is for and it looked fine. I have been cleaning that sensor since ive owned the car which has been almost 15 years or so with no problems. I just now notice everyone says we shouldn't be cleaning them. Anyhow I don't visually see anything wrong with it.

    One thing that makes me feel like its a bad sensor is because if I disconnect it while the engine is running, nothing changes. Is that normal?

    Like I said, I can now drive the car and it has power but while driving and coming to a stop it hesitates as if its going to stall but doesn't.

    Besides replacing the air flow sensor, is there anything else I can try? I'm so close to being able to drive my car, any help will be greatly appreciated.

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  3. #2
    Great White mysupratoy94's Avatar
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    Nov 2003
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    Duarte, CA
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    Quick update, I received a new MAF sensor from eBay. I installed it and the car won’t start with it installed. I removed it, installed my original one and the car started right up. It still up and down from like 400 rpm to 900. If I accelerate it does so smoothly. Just on idle it fluctuates. Again, if I remove the connection from the sensor nothing happens.

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