No where near enough info
does the noise vary with revs
half engine speed
has it a lack of power
petrol or diesel
ect
could just be a bad injector
cheers
blaze
Is it the 4.2 1hz diesel? Could be any of the following, loose or split vacuum hose, water in fuel, air cleaner blocked, exhaust manifold cracked or loose, tappet adustment, injector pump, fuel filter, could go on but You need to look at the basics first, as said not enought info.
John
Simple, take it to a reputable diesel mechanic and pay them for a proper investigation and report. It may save you money getting to a problem before it get more expensive to fix.
I was a mechanic and worked on diesels but I would not attempt to tell you what may be the problem on a forum, even with more information. Running with a bad injector may do serious damage. As will water in the injector pump. Or a lot of other things that might be able to be easily corrected early.
My two cents worth.
Jaahn
-- Edited by Jaahn on Thursday 28th of February 2019 07:53:46 PM
I used to be the proud owner of one of these, used it as a Charter Vehicle.
I totally agree with the replies already posted. There really are too many variables.
EG. the motor was running real rough one day; shaking its head and lacking power. Problem: a tiny stone dent in the fuel filter, and was sucking "just" a little air!!!!
However, you need to find a "Good" mechanic that is willing to spend the time to do the trouble shooting.
If you get a mechanic that is just guessing it possibly will cost you a heap of $.
How much blowby out of crankcase? A bad injector or air in system can sound like detonation on petrol engine . When was it last serviced , fuel filters etc ? Oil pressure, oil consumption ok ?
My error should have given more information. engine is very noisy at idle and vibrates a lot. It is a 6 cylinder diesel, also seems to blow a lot of black smoke when revved
I am thinking injector, if you are able to crack the injector pipe nut at the injector, one at a time, that will isolate it to a cyclinder cheers blaze
ps
also check ypor air clwaner and any flexable inlet hoses between thhe air cleaner and the inlet manifold
-- Edited by blaze on Tuesday 5th of March 2019 10:39:58 PM
Say its in need of rebuild ? Check harmonic balancer. Injectors . IP maybe turned too high . Sounds like some cylinders are down on compression ? May have had petrol through it ? With broken rings being the result .. Is injector timing set right ? Sounds like it could be retarded ..!
It may save you money getting to a problem before it get more expensive to fix. 
Or a lot of other things that might be able to be easily corrected early.
