Rough idle on 2001 nissan altima. Runs great then seems to fall off, will then regain normal idle speed.

1. Change fuel filter.
2. Change spark plugs--replace platinum plugs at half the recommended mileage.
3. Check for any vacuum leaks.
4. Check EGR valve.
5. Check engine timing.
6. Check for weak ignition system; e.g. distributor cap, rotor, coil, and plug wires.
7. Add fuel injector cleaner.