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2004 350z, unstable / low idle when engine warms up

Home Forums Stay Dirty Lounge Service and Repair Questions Answered Here 2004 350z, unstable / low idle when engine warms up

This topic contains 1 reply, has 2 voices, and was last updated by Nightflyr * Richard Kirshy 1 year, 9 months ago.

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  • #963215
    Erik Peters
    Erik Peters

    Hello all, I’m coming to this forum out of lack of answers from reddit and the my350z forums on a peculiar issue with my car. My 2004 350z was out of operation for about a year while I painted it, and it always ran great. Upon returning the car to regular operation, I filled the tank for the first time in a year with the typical premium gas at shell. The next day while at a stop light I noticed my engine stalled due to dropping rpms. It stalled 3 more times on the way home, and I noticed a burning smell in the cabin. I popped the hood and heard what sounded like a crackling fire, but there was no flame. I let the car sit for 6 hours, and upon restarting the car cold it was completely normal. I figured it was possibly my throttle body or MAF, so I gave both a quick clean, and forgot to unplug the negative terminal before unplugging either. After that, I drove the car to see if it rode any better, and unfortunately got stranded on the road as the car refused to fire up after stalling at a light. I towed it home, and got 2 codes; p0300 and p0302. I took apart the valve covers and found a lot of oil in cyl # 5, practically submerging the spark plug. I replaced the valve cover spark plug seals and dried the oil, and replaced the spark plugs. After putting everything back together, the car had trouble with warm idle, and when turned off when warm, would not fire up again. The next day I replaced the camshaft sensors, and didn’t have much improvement. I just replaced the pcv valve today, along with its hose, and while the car was now in acceptable idle ranges, it was still spotty, and had the idle rpm jumping from 600 to 700, pulsing every few seconds. After letting the car sit, the car stabilized to 650 rpms, and stayed like that. The scanner reported no codes, but showed the following values ;
    [COLD] ECT is 33 C, IAT is 28 C, MAF reads 7.86 g/s, O2B1S1 reads 0.295, O2 B1S2 reads 0.28, O2B2S1 reads 0.59, and O2B2S2 reads 0.28.

    [WARM] ECT is 95 C, IAT is 30 C, MAF reads 3.68 g/s, O2B1S1 reads 0.32, O2B1S2 reads 0.73, O2B2S1 reads 0.59, O2B2S2 reads 0.79.
    I am now too hesitant to drive the car very far out of fear of having to tow it again, and have not resolved much other than a copious amount of oil in my cylinder 6 and its misfire. I was planning on replacing the following items in the following order; Crankshaft Sensor, MAF sensor, EVAP Purge Valve, Fuel Injectors, Fuel pump. A part of me thinks it’s bad gas, but I’m not too sure how common it is to get gas from a reputable station like shell. I’m running out of ideas and need the car running, if anyone has any suggestions they would be greatly appreciated. Here is an example of the unstable idle:

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  • Author
  • #963216
    Nightflyr *
    Richard Kirshy

    You need to determine what exactly your missing when the engine fails to start when warmed up before firing the parts cannon..
    Are you losing fuel pressure, are you losing the fuel injectors, are you losing ignition (ie spark)
    Find out what your missing, then work from there.

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