525 tds erratic idle/ power increase black smoke

[gregyboy]

Hi guys, first timer on here, love the look of the site, wonder if any one can help??
I have a 525tds 1995 model with about quarter of a million miles on the clock!
This car has never let me down, oil/filters changed over regularly, however it has developed a problem. ----here are the symptoms;

Erratic idle almost like a missfire when driven, goes like smoke, however there's plenty of that as well, as in clouds of black.
now I've cleaned the EGR when you disconnect the vac pipe, it runs marginally better, reconnect and give hard throttle there is knocking as in overfuelling. I've changed fuel/air filters, pump in tank putting out correct pressure
can anyone help ??
any advice??
Thanks in advance Greg

[marti5]

Injectors are coming to the end of there life, I would suspect with 1/4 million miles on the clock.

[gregyboy]

Thanks marti, surely I'll check/test them, but why do things change when the vac pipe to the EGR is disconnected, clearly it is overfuelling, but surely not on all six (i.e six injectors).
thanks again Greg

[MADDOUG]

Sounds like classic injector trouble but get codes read as it may be temp sensor failed as well causing it to run rich