55reg td4 104,000mls overfueling

hi all , having engine running issues 1500-2000revs engine knocking rattleing not all the time., can run for days no problems then next day its there, went to main dealer to book in for diagnostics check can only do it next week,while there i was talking to a mechanic/technician he says its overfueling thats whats causeing the problem diesel knock, just asking anyone for ideas , to prepare myself for the size of bill, ill keep you posted of the outcome,

he says its overfueling thats whats causeing the problem diesel knock

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would have thought that 'overfueling' might be accompanied by other symptoms
such as lower mpg 'n higher emissions .. maybe black or grey exhaust smoke

be various reasons why a td4 might 'overfuel' ..
some failing maf sensors cause overfueling instead of the opposite underfueling ..
( .. Maf sensor problems. .. )
injectors / fuel pressure sensor / fuel pressure regulator .. etc etc ..
might have thought with the latter .. if faulty .. that there probably be additional symptoms

extra diesel 'knock' could easily be just fuel quality ..
e.g. the fuel cetane value is too low
maybe more apparent before the turbo is really boosting
i.e. lite-foot partial go-pedal condition

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anyhowz .. diesel 'knock' is explained on the following webpage:

The quiet diesel evolution

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hi hd3
thanks for reply as i said booked in at main stealers, mechanic there told meabout a mech/tech that had left there to set up himself so i give him a visit, he hooked up to t4 diagnostic that showed 1 injector out of spec at idle and 1 injector out of spec at 1200 revs different cylinders, so now in the process of 4 injectors refurb ill let you know the outcome,

good that the cause has been identified

curious to know what might cause an injector to go 'out-of-spec' within a specific rpm range .. the electronic side .. the mechanical fuel-pressure side ..
or a combination of the two ..

i.e. anything i might know about common-rail injectors be gleaned from google

e.g.

injector internals
Bosch TOP4 CR Piezo Injector video - Teknik Dizel - YouTube

How Bosch Piezoelectric Diesel Injector Works
How Bosch Piezoelectric Diesel Injector Works - YouTube

Hi all, update for the problems I 've been having 4 injectors been refurbed by lynx diesels as recommended by rover Ron.now running sweet again.