driving back from florida yesterday,with the cruise set at 85 mph all of the sudden you would here the noise pitch change,not accelerating or anything,rpm's would stay steady,just you would hear the noise of the motor change??


it would not do this everytime just out of the blue and all times it was above 80 mph,with or without cruise??all guages were fine no check engine lights nothing to say there is a problem but you definately could hear it change..http://www.dieselplace.com/forum/smileys/Confused.gif


any ideas of what would cause the tone to change?i only have 2000 miles on it..

Sounds like pilot injection (PI) turning off and on. Mine goes off about 2500 RPM and then will come back on when the RPM drops down to about 2200. If that is what it is, it is normal. I'm not sure since I don't cruise that fast, but 85 MPH has got to be right on the edge of the PI envelope.

thank you..i don't normally cruise that fast but traffic was really haulin,any slower and you were constantly changing back and forth lanes because the slow lane was slow..


thanks again i feel much better..http://www.dieselplace.com/forum/smileys/Big Smile.gif

toolman:


It is a bit disconcerting the first couple of times you hear it! I can't describe it better than to say when PI turns off, it sounds more 'diesely', that is, more diesel rattle. I suspect that after the PI turned off, as the load on the engine changes just slightly, you hear that.