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P0306, but only appears every few months.

840 Views 10 Replies 3 Participants Last post by  mikemaj82
Every few months I seem to get a P0306 cylinder misfire code while driving. When I get home, I'll reset the code with my XTool D7, and it won't come back for a while. It seems to be in 2-3 month intervals. I don't feel any vibrating or hear anything different when the code is active, and the idle is normal. Just wondering why this would happen randomly. If it were a true misfire, the code should come right back after the reset and starting the engine again. If it happens again, I'm going to swap the coil with the one next to it, and see what happens. The car only has around 49K miles, and the spark plugs were changed about 2 years ago, and I put in Accel coils about 3 years ago. The only other thing I could think of is a possible issue with the injector or the wiring harness in that area being pinched.
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Thanks. I'm probably gonna just start with a coil. The code hasn't come back since this post.
Yea if the code comes back one more time that's what I'm gonna do.
It just came back today. Apparently, there is a surefire way to get it to come on. If the car is not yet at operating temperature, and I give it heavy gas from a stop, it will come on immediately. Happened twice like that now. If the car is already warmed up, giving it heavy gas will not cause a CEL.
This is good information to know. Not 'stone cold', but maybe 100℉ - 150℉ (37℃ - 65℃)?
Are these the correct OEM spark plugs?
So apparently this one was a false alarm. By the time I was able to plug in my scan tool, the code had disappeared, but what was stored in the history was P0523 Oil Pressure Sensor Circuit High. This is another code that I get intermittently...every 3-4 weeks or so, on hard acceleration. The switch was on an aftermarket oil filter adapter housing that I got on Amazon, but I did save the old sensor so if it gets to the point where it becomes a permanent issue, I'll just swap in the OEM sensor.

But to answer your question, the spark plugs were replaced about 5,000 miles ago with Champion plugs...same ones that I pulled out. And I am the original owner so that's what was in there from the factory. And yea the temperature was probably closer to the lower range you posted.
Yes I can record live data with it. I'll see what I can get.
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