Hi I have the same issue as described previously. I only have 35k on the clock and use the vehicle to tow a big boat to the ramp and back a few kms away. Oil change every 5000k and filter too. Fuel filter every 10,000k. Never the less, 1500rpm loud metal knocking left rear of engine, dissipates after 15 minutes. No smoke no loss of power. Only started in March / April conveniently just before the warranty ran out. Reported to dealer several times and each time told "completely normal". Well it is and it isnt isn't........
Researched on web / forums etc. First thought was possible sticky valve lifter. Did oil flush, correct weight oil, lifter free etc etc - no difference. Seems it could be injector since this is a very, very common problem for D4D engines including Hilux and Prado since Toyota brought in CRD. Have a look, there are hundreds and hundreds of angry Toyota owners and all have the same issue of loud knock as a result of failed injector and Toyota not admitting problem with injectors. Also seems that CRD's DO NOT suit low kilometres and short trips - so should have bought a petrol or stuck with the old indirect 80 series......
Demanded injector test from dealer and after overnight stay they returned one piece of paper with hot results only, that showed all injectors in tolerance (worst -1.1) and said "see normal". Demanded cold test results and they wouldn't give them to me saying it is flight recorder data logging and not possible. Offered to trade the vehicle in for good price since they said it was perfect but they wouldn't be in it??? Complained to Toyota Australia. A little while later dealer service manager rang back and admitted cylinder 8 on left rear is -3.3 at cold. No resolution - just dealer is talking to Toyota to further analyse results to see what can be done - yeah right!
More research. Seems pre 2012 Denso injectors have two problems 1/ copper washers self destruct 2/ injector spindles suffer from premature wear and either stick open or closed. ECU compensates and puts more fuel in or starves of fuel so noise is actually (like petrol) timing/advance/pre ignition and because very high compression = very loud knock. Left unchecked and piston can crack or melt (this has happened to some according to the forums). Solution is to replace all injectors - not just the affected one, since it will only happen again (see forums). Two options for new injectors = Denso OEM which NOW (post 2012) have a DLC (diamond like coating) (see also new 2016 injectors on Cruisers and Prados ) OR reconditioned injectors through a mob called Baileys (called 'Blueprinted' which also have protective coating). Each cost around $500 - $600 each from Diesel mechanic or >$1,000 from Toyota plus labour to install and it is a minimum 10 hour job.
So, stuck with this mess, I have booked my vehicle in with a diesel guy (definitely NOT Toyota) and will have the injector test done properly with a view to replacing all injectors which will hopefully give me the 200k plus kilometres I originally intended. Hopefully the piston is ok but will need to do camera inspection when injector is out. Cost of re-build or new engine I see is around $15 -22k so $5k or $6k for injectors is a bit better?????
I'd like to hear from anyone who has 'survived' the injector change out...........
