300 TDi failed MOT on emissions, got a 3.78 need 3.00

[Zedman]

I am just getting ready for the year ahead and went for the dreaded MOT all went well, needs new pads on the back and a front bearing tightenig up a tad and a head ligh adjust but the deal breaker was the emmision fail
Its a Defender 90 about 1999 on a Q pate, 300Tdi no electronics.
Got a 3.78 need 3.00 I have put injecter cleaner in the fuel an run it for a cuple of hours, done an engine oil flush with a cleaner then changed the oil change + all filters.

Is there anything I have missed that may be causing the issue and I can sort before putting it in for the re-test, all help appreciated.

[Matthews]

Turn the fuel pump back down , last time I followed you I was amazed at how much black smoke you were throwing out . (It must be bad for me to think so !!!).
Matthew

[nicks90]

Never had any success with injector cleaners in the fuel. If they are gummed up, only sure fire way of sorting them is to recon / replace.
Alternatively you can run the engine at a fast idle and spray a fine mist of water into the inlet manifold. If its carbon build up, this should clean it up,, but if its the jets themselves, no option but to get it done proper.

But if the fueling is way too high, it'll smoke no matter what, like Matthew said - wind it back a bit.

Nick

PS. Use only a little bit of water, maybe 50ml and on a fine spray from something like a windolene bottle. If you think I'm mad, just look for pictures of a cylinder bore from and engine that's had a head gasket failure - shiny and clean! You'll be spraying much less over a minute or two and it 'shouldnt' damage anything. Also had added benefit of de-gumming the bores and cleaning the valves.

[Dave]

As far as I know, and being the owners of a Q-reg 300Tdi, There is no emissions test on a Q-reg vehicle, only a visible smoke test.
Dave:

[Bobcat]

This might be a silly question but, when did you last change your air filter ?