165k miles on OD, 4400 hours on engine, and 15K miles on new injectors, no stored P-codes.

I've developed a throttle-pressure sensitive engine speed noise that is not quite like a tock-tock-tock. Its somewhere between that and the sound of a big compressor, once per engine revolution, I'd say. The noise will go away with less or more throttle pressure but is pronounced at highway cruising speed.

That noise, and what makes me think its running lean, is that if I coast down an off-ramp, say, and then give it moderate throttle after the stop sign the engine will issue a brief noise that I can only liken to a lean-running gas engine suffering from pre-ignition, a soft machine gun flurry of rattles when starting off the line, but not like a normal diesel engine rattle. The engine in general just seems noisier as well.

I would also say that my power's down some. I used more throttle when last pulling my fiver than usual on the same local roads. Boost and exhaust temp are fine, but I don't have fuel pressure gauges or a scan tool. I put in a Napa Gold fuel filter about 2K miles ago and I'm going out now to put in a Baldwin 7977 that I usually use. Any thoughts?

 

The air-compressor noise is coming from the intake. It's more pronounced when I took the air-box apart. More of a Puh-Puh-Puh noise.

 

Sounds like a bent intake valve to me.

 

Since the injectors were done have you checked your valve-lash?

 

A diesel doesn't run a ta fixed A/F ratio. It varyes with the throttle and load. From 80 to 1 down to maybe 12 to one.
You are possibly hearing injector rattle and this can be a bad load of fuel to injector issues etc.

 

Thanks, its going in under the scope in the morning. I don't like being four time zones away at times like this but my wife's a trooper and I need it fixed before the weekend. I so love this woman who'll take the truck to a diesel repair shop for me.

 

AND its a LEAN RUN MOTOR!!!!!! it runs as lean as it can!!


sounds like time ing (? help on that one ) rattle to me.