[GTP Dad]

Check the Crank Position Sensor. It is probably going bad and not sending a proper signal to the computer. The only other thing is to check the EGR valve which could be blocked and causing you problems. They only work when the engine is up to operating temperatures. If the passage gets blocked the car will run badly. They are not hard to clean and most generally will not send a signal to the computer and give an error code until they stop operating entirely.