help me fix my mums car! idle and running issues! vn v6!

[VNexecutive]

heres the dilemma, the car (series 1 vn v6) will start and run perfect, it will rev fine, till it starts to warm up. then it goes downhill, cant rev it without it coughing and spluttering, cant put it in any gear without it stalling, etc. fuel pump primes fine, and the car starts every time regardless of how bad its idling.

so far i've replaced:

new fuel filter
new crank angle sensor
changed the series 1 coil pack to the series 2 one
changed the fuel pressure regulator
cleaned the throttle body with carby cleaner or whatever its called
changed computers with no result


i have a second hand o2 sensor to change tomorrow and try that, but otherwise im stumped!

should i swap my 5L throttle body onto it to check the sensors on the throttle bodys? i suppose if it starts running fine it could be the TPS?

also its not blowing any smoke, but it is using more fuel than it should by my calculations, 360 kms to the 65 litre tank on last fill.

any help would be handy cos im racking my brain, im losing hair, and about to go on stress leave..

thanks

PS: i did the diagnostic check and it came up with code 12. go figure!

[Brett_jjj]

Id try doing a diagnostic check to see if any error codes are logged.This test only takes a couple of minutes to do yourself, and might point you in the right direction to whats wrong.If you dont know how to do this test ,just find the plug in the pic under the glove box in the corner.And use a paperclip or a piece of wire to join the 2 contacts as shown in the picture in red.Once the two contacts in the plug are connected,turn the ignition key to on,(dont start the engine though),and the engine light on the dash will flash on and off.These flashes stand for a certain codes.Like one flash,followed by two flashes,will mean a code 12.If you get 3 flashes,followed by 6 flashes,you will have an error code 36 and so on.I think each code is seperated by a longer pause.And code 12 will be flashed continously if there are no logged error codes.Let us know if you get any codes showing up.We can tell you what the code is for,or you can just search VN/VP error codes on here.
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[strgas]

check your base idle

[Lost_Pete]

Could a bad fuel pump. It can still run but doesn't provide enough fuel pressure.

[VNexecutive]

thanks for the replies guys, turns out its more than likely a bad fuel pump. only has about 10 psi of pressure at on(priming), idle and under acceleration.