engine

In some cases, when the engine "warms up", it enters into a status called "closed loop" in the engine's processor. This is when the processor starts looking at sensors and engine information to run the engine most efficiently. Therefore, something in the engine management is not functioning as it should. A diagnosis is necessary to determine the source of your failure. I would look for obvious signs of an air intake leak (like a broken air box), or a vacuum leak in the engine compartment area. Good luck.