Question: I have a honda city 2006 model, I recently changed the fuel pump motor cause the car was jerking when the fuel was low but after 1 month the same problem has occured. What could be the problem?
Answers: The engine jerking can be due to the ignition system misfire, lean misfire, & mechanical misfire. - Ignition misfire : As the spark plugs, ignition cables, distributor cap and rotor, and ignition coil wear over time, their ability to transfer the needed spark to ignite the air/fuel mixture inside the combustion chambers becomes less. Initially, the spark will only be weaker. As the ignition components continue to wear, the misfire will intensify and the combustion process gets interrupted. - Lean Misfire : Imbalanced air/fuel ratio (too much air/too little fuel). Since an engine needs a richer (more fuel) mixture for a smooth idle, this problem may be more noticeable when the vehicle is idling. An EGR valve that is stuck open, a leaking Intake Manifold Gasket, a defective Mass Air Flow Sensor, a weak or failing fuel pump, or a plugged fuel filter are some of the many causes for a lean misfire. - Mechanical misfire :Check the worn piston rings, valves, cylinder walls, or lobes on a camshaft; a leaking head gasket or intake manifold gasket; damaged or broken rocker arms; defective fuel injectors and a slipped or incorrectly-installed timing belt. It can also be due to vapor lock in the fuel pump motor which results in jerking.