Possible Causes

WARNING: This page is about a different car, the 2003 Mazda MPV and 2002 Mazda MPV. However, it is still accessible from the selected car via links, so may be relevant.

Fuel injector malfunction.
Ignition coil malfunction.
Intake air system leak (between dynamic chamber and cylinder head).
Low engine compression.
Spark plug malfunction.
Wiring or connector and terminal malfunction.