I will start out by saying I know about all the "normal noises" said to have been heard on a DMax and I have scoured the forum for answers. I should add that I have always been paranoid since my first car. I run B5 and I added about .5 oz per gal. of low ash lucas 2 stroke oil the last 2 tanks to see if it helps.

Here is whats going on:

Its hard to figure out where its coming from even with a scope. The noise is almost undetectable at idle in park but you can hear it if you punch the throttle. It becomes very clear especially the chirp under load in gear and becomes louder the more the engine is loaded. While driving the noise all but disappears when I am cruising and take my foot completely off the throttle. This noise has been there since my fuel system mods but it has been intermittent and never this noticeable. It kind of sounds metallic like a valve out of adjustment. Performance, smoke, milage, EGT are all unchanged.

Testing lately with an amplified scope but cant isolated the noise. Hooked up EFI and check injectors and all rates are +- 2mm3 in park and even out once in gear. Shutting each injector off while in gear and here is the interesting thing. Naturally each cylinder will knock a little when the injector is shut off, when I came to num. 8 the noise got louder and was pretty much in sync with the normal cylinder knock.

My thoughts are I have a noisy and annoying injector but its functioning properly and just bugging the s*** out of me.

Looking for some advice before taking to the dealer or swapping injector.

anybody?

Ear plugs and 5 milligrams of valium will make all that go away...

bump

Sounds like a fuel noise, if its since your mods then you have your answer. could the chirp be a exhaust leak, heard many sound like that before and fool tons of people.

Thanks. I am gonna spend the day tomorrow listening with the scope to see if I can find anything. My gut is saying I am just fine. The truck only has 16k on it and I very seldom run over nicks 430 tune.

My lmm had a faint chirp chirp chirp under hood at idle.

Turned out to be the shiny smooth label in the serpentine belt every time it came around and slipped a little on the smooth side of a pulley

Try putting the stock tune back in. See if it still happens. This would let you know whether it is something affected by a tune. Technically, it would probably let you know whether it was belt/pulley related or engine related.

Is the sound consistent on all 5 of you tunes? I left one of my tunes as stock and you can't hardly tell it is a diesel. On any of my customer tunes, you can tell readily there is timing added.

You did the PCV re-route, assume no blow by showing?

If you are worried about engine integrity, you could take an oil sample and test it. If you have something amiss with #8, it should show in the oil.