front engine

What is your question?

The car is perfectly running when the engine is cold. After about 10-15km running, then the problem arises where the car is experiencing jerking and loss of power. What is the problem?. However, it is no issue on idle during either cold or hot engine. Note 1. Fuel pump is already replaced new 2. spark plugs are already replaced new (4 nos) 3. Plug's cable is new and tested OK.