* Clogged fuel injector or carburetor
* Low fuel pressure
* Faulty fuel pump
* Ignition system:
* Faulty spark plug
* Bad spark plug wire
* Weak ignition coil
* Valve train:
* Bent or broken valve
* Leaky valve seal
* Cam timing:
* Advanced or retarded cam timing
* Compression:
* Low compression due to worn piston rings or valves