I have an engine misfire when engine is cold. If its put into reverse with foot on brake, you can hear a knocking noise that stops after engine warms up. Thanks.
A consistent engine misfire will eventually cause the check engine light to illuminate. Once the check engine light has come on and stays on the first step would be to pull the engine trouble codes. These Engine trouble codes will indicate the exact cylinder that is having the issue. This will make it easier on the wallet instead of throwing parts at it.
A knocking noise is not good. If it is being caused as a spark knock it may be as simple as contaminated fuel. Once the engine warms up the knock sensor is able to correct the engine timing and prevent the engine knocking noise. Once the fuel tank is below half full try filling up at a different fueling station with the Highest octane available. This will mix with the fuel already in the tank and raise the octane level. You may need to do this the next couple of fill ups. I think this would be the best first course of action.
Internal Engine Knocking Noise
Rod knocking is referring to the engine rod bearings falling. This causes an engine knocking noise that generally will get louder when the engine is revved. Normally will become more pronounced once the engine is warm. I do not think this is the case with your engine but thought I would share for other readers.
A Main bearing knocking noise refers to the engine cranks main bearings failing. With the main bearing failure the knocking is more pronounced at engine idle. The engine knocking noise will tend to go away when the engine is revved. Normally will become more pronounced once the engine is warm. Again, I do not think this is the case with your engine but thought I would share for other readers.