2006 Lincoln Navigator P0430 Code
 

one month back i got CEL on. computer check revealed one ignition coil not working and fuel pressure sensor fault. i changed the coil and after 2 days CEL again switched on. on checking there was another coil damaged and o2 sensors problem. i changed all plugs and all coils. After one week CEL again comes up. now there is P0430. kindly let me know what shall i do ?

There are three main reasons for that code. An exhaust system leak on bank 2 cyls 5,6,7, & 8 or oxygen sensor (after converter) not functioning properly or catalyst not doing its job. If you Google that code it will provide the many reasons for it.

@ hanky , I checked fuel sensors and fuel pump as well as o2 sensors from computer (VCM diagionastic tool) and all are fine. the o2 sensors are mentioning rich -lean-rich-lean...... . but mechenic says that they are fine.

The info you are getting is incomplete.
The downstream oxygen sensor should not be doing as you have stated.
There is more to diagnosing these problems than reading from a tool. You need to know how the system is supposed to work and be able to interpret the info the tool is providing.

dear,
can installing spark plug non fouler on post cat O2 sensor will finish this code.

I wish it was that simple!
The readings at the post cat sensor are affected by what the upstream sensors are seeing and correcting. Also an exhaust leak anyplace before the sensor(s) can affect the results and require thorough examination to eliminate those possibilities.