no sorry foot doesn't need to be on clutch nor does it have to be stationary but when revving it makes noise and whilst driving and suddenly accelerating it pushes out black smoke

Thin you better get a compression test done asap. Maybe get the top cover/cam cover off as it sounds mechanical. Just in case issue.

its an injector apparently just need to find out which one

HiYa andyeastsussex,

Testing, cleaning, changing etc there are lots of youtube howto's to get some idea of what your are dealing with. If you are anywhere near tfb he might be able to test them for you. Best of luck my friend.

You might get away with disconnecting the electrical connections to the injectors one at a time...whatever you do DON'T undo the fuel pipe, it's very dangerous. I can do a leak back test on them but that may or may not show anything.

Another trick is to use a stethoscope or failing that a long screwdriver held against your ear!

Regards
Richard

hi tfb where about in country are you ive tried screw driver test but I cant really tell any difference not sure what im suppose to listen or hear

right ive just been out to car disconnected the plug to a injector but wouldn't fire up so couldn't test it that way :(

I can confirm that diesel injectors CAN make a clicking noise when delivering more fuel, I had a Renault Megane that did just that. They were solenoid injectors, same as GV. It could well be the solenoid on one injector is clashing on something for some reason.
Maybe your best way out of your problem, if it be an injector, would be to buy a recon. one, then substitute it for each injector in turn. Fingers crossed...

Leedsman.
n.b. If it be an injector fault, it will be the last one you substitute. (Sod's law).
Also, the black smoke you mention is another pointer to injection problem.
Safety factor:
Make sure the nuts for the high-pressure fuel rail which runs at 25,000PSI approx. are done up properly.

Most quality mechs / engineers carry a spare known to be good for just that Q&D test. Its P&P anyway so not a problem - unscrew then plug in the known to be good and if it cures it there's no need to look further - hence the quick & dirty test.

I'm in Cambridgeshire, I would guess by your username it would be a fair trip to me.

While it's running try disconnecting the electrical plug to an injector, can't remember off the top of my head if the ecu will kill the engine or not. Might be possible to fool the ecu into thinking the injector is still connected by using a resistor or plugging in to a spare injector. The injectors are of the piezo type.

The cheapest spare injector on Ebay is about £50 and should be OK for testing with, 2.8 and 2.5 injectors are interchangeable.

Regards
Richard