Well...it sounds like valve/lifter noise???

[AEmedic]

I have an 02 with the d/a and from about 1500 rpm and up it sounds like the lifters make all kinds of noise, it's louder under load and it is worse as it warms up. The truck seems weaker than it should, but has none of the other symptoms of injector failure(smoke, fuel in oil, or high return rates).
I took it to the dealer and they say that it is all normal, but it does not sound normal to me for a dmax with 83k miles on it.
Any Ideas?
Thanks in advance,
Chris

[WILLYD-MAX]

Sounds like your pilot injection is turning off, and it does sound loud but usually mine does it at more like 2200rpm and up.

[mark45678]

pilot injectors should not be turning off until the motor is over 2600 and light loads is the only time you will know its off , if your asking for power above 2600 rpm you will never notice any change. The newer lly and lbz truck seam to have smoothed this transition point out so its almost not noticeable....

[More Power]

I would imagine a mechanical problem (with a lifter or valve) would produce a noise more or less constant in volume no matter the load, except the sound would change in pitch as rpms increased/decreased.

Since you mentioned "louder" with increased load, I would tend to focus on an injector. Might be time for an injector balance test...

GM has modified the pilot injection programming since the first 01 was introduced - producing a less pronounced effect. My 01 makes less noise under load now after the programming was updated above 2500 rpms than it did when new.

Jim

[AEmedic]

Thanks for the reply! I had the dealer change the fuel filter when they ran the diagnostic on the injectors (balance/return rate both are supposedly normal). The noise is unchanged following the filter change and fuel injector cleaners. The dealer tells me that 02's are just alot louder than the others and that is's normal. I think they just don't want to work on my truck. :confused:

[AEmedic]

I forgot to mention, it is actually quieter over 2500 rpm than between 1500 and 2500 rpm.

[AEmedic]

Well, I went to another dealer and they agreed to change all the injectors under warranty and I should have it back tomorrow if all goes as planned. I just had to take it to a dealer about 100 miles away.

[More Power]

In the earlier mechanically injected 6.5's, the diesel rattle would diminish as boost pressure rose. Your engine sounding quieter at higher rpms was probably accompanied by more boost pressure as well.

Did the dealer tech perform an injector balance test? Or, did he base his diagnosis on something else?

Jim

[AEmedic]

Honestly, they didn't say why they were willing to do it and I didn't look too deeply into the mouth of the gift horse... I'm just glad they are doing the work for me.

Chris

[AEmedic]

Well, just got back from Helena, MT and the truck runs better than ever. It is SO quiet!! Lots more power than previous.
Thanks to Lithia Chevrolet, all eight injectors and many of the fuel lines were replaced. It completely solved the problem.

[More Power]

That's good news! Thanks for the followup. :)

Jim