Car Knocks and shuts down

Dear Carpros!
I have a nissan maxima model 2003. 3.0J
whose mechanical specifications are as follows:
Transmission: Manual
Engine: VQ30DE
Type: 6-cyl. V- information DOHC, Water-cooled
Bore x stroke mm: 93.0x73.3
Compression ratio: 9.5 to 1
Fuel system: ECCS, (Electric Concentrated Engine Control System)

Problem:
When I start my engine it starts nicely. But as it starts warming up the engine knocks and it seems as the fuel supply has been blocked. RPM drops and after few seconds it increases and geos up in between (2000-3000). If I dont pump the engine goes off. And when I try to switch on it takes lots of pumps and I have to keept the ignition switch on which is damaging my self and battery.
Also it is giving black smoke.
Kindly guide me in this regards.
Do I need to change any parts?
I will be waiting for your quick reply.
Best Regards,
Adil Pervaiz