2003 Mazda Protege5 - Hesitates during acceleration

My car has 116,000 miles on it, is a manual transmission, and I’ve owned it since it was brand new in 2003. The car has been absolutely wonderful, and I try my best to take care of it. A couple of days ago I noticed that the car hesitates during acceleration around 3k RPM like it’s not getting the right amount of fuel into the motor. Last month I changed out the spark plugs, coil packs, EGR valve, spark plug wires, and cleaned the K&N air filter. The car hasn’t had any issues whatsoever, even after driving around the USA and northern Europe with the car. I perform (or have done for me) routine maintenance to make sure the car is always in good shape. Could the fuel pump or fuel injectors need checking or replaced? The car doesn’t have an in-line fuel filter, so I can’t replace that as it’s “part of the fuel pump unit and is not a routine maintenance item” (Haynes Repair Manual). Can I use an additive to temporarily clean out any stoppage?

The fuel pressure/volume should be tested.

A weak fuel pump can be on the hairy edge where it doesn’t deliver the proper fuel pressure/volume when power is demanded from the engine. So the engine lays down.


Agree w/Tester, pump and rail fuel pressure should be tested first. Ignition system can cause this symptom too. Problematic spark plugs maybe? Were the new plugs verified to be what the owner’s manual recommended for this engine? Gap verified?