Engine misfire only when car is hot

Question

I have honda civic 2011, now it works fine when cold startup and dont give much issues other then when I "accelerate a lot" and having done that for a while, the car starts misfiring.

Now the solution i use to fix this is to replace spark plugs each year so my problem, hence subsequent question is about the phonomena only:

Is it the fact that spark plugs when heated a lot starts to malfuncion or is it something else? Because replacing new spark plugs enable me accelerate a lot without issues. The most curious and confusing part is that the next day the car appears normal again under normal load, it will start misfiring if I accelerate alot (putting the car into misfiring phase) and then even at slow speeds without accelaration it will misfire! Another funny thing is during acceleration itself, the car dont misfire, so the only way after it has gone to misfiring phase is go press gas pedal a lot when its misfiring so more fuel gets rushed in and it revs up the engine and misfiring goes.

Also when car goes into "misfiring phase" then misfiring happens a lot while idling!

And next day if I drive car without significant acceleration and stay at low speeds, the car works fine.

So I am assuming some phenomena related to spark plugs

Answer 1

Just a guess really, but one possibility is a faulty injector.

If it is not injecting fuel correctly it could be making one cylinder run a weak mixture. This could overheat the one cylinder and the spark plug causing the misfiring.

Under heavy acceleration the ECU runs the mixture richer which for the faulty injector will bring the mixture out of running lean.

An OBD2 reader may indicate which cylinder is misfiring.