Q: Cylinder 5 has a misfire.

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Today I checked my cts2 diagnostic reader and it popped the code p0305 (cylinder 5 miss fire). It doesn't idle rough or like stutter step. It has full power and when I checked the diagnostic a few hours later, it doesn't come up. I really haven't found anything online or anybody I know in person that has a clue. But I do know one of my injectors or a sensor is going bad, no matter what the air temperature is outside, if my truck goes into high idle and the coolant temperature is from specifically 65-100degrees it has a rough idle and white smoke pours out until the coolant temperature hit 100. My coolant could be 25 degrees and high idle kicks in but it doesn't rough idle until it hits 65. Thanks for your time

My car has 124879 miles.
My car has an automatic transmission.

Hi there. To determine if the injector is not working properly, either you can perform a cylinder cut out test on your injection system or you can swap your injector on cylinder number 5 with another cylinder and see if the code registers a misfire on the other cylinder. If the other cylinder changes or if the cylinder cut out test has not change on cylinder 5, then the injector will need to be replaced. If you move the injector and cylinder 5 still has a misfire, then there could be a burned exhaust valve that is cause a loss of compression until the valve heats up. It maybe a small amount of material removal on the valve causing the misfire. If you need further assistance with your engine misfiring, then seek out a professional, such as one from Your Mechanic, to help you.

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