Q: Q: Car misfires

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My car misfires, but that goes away after revving the engine a couple times.

Hi there. Though misfires can be caused by a number of reasons, a misfire that is present only when the vehicle is first started only has a few common causes. Most of the time this is caused by oil or coolant leaking into the cylinder when the engine is off indicating an internal engine problem. This includes a valve seat that is failing causing compression to be low until the engine warms slightly, or a leaking fuel injector allowing fuel to leak into a cylinder when the engine is off. All of these will cause cold misfires. As a mechanic I would typically do a cold compression test first to identify any internal engine problems. If that does not show anything, then each spark plug needs to be carefully inspected to see if there at signs of fuel or oil fouling. If these are not tests that you are comfortable with, I would enlist the help of a certified mechanic, like one from YourMechanic, to inspect your misfiring vehicle.

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