Engine/Transmission (1998.5 - 2002) engine sounds funny

[bud kohn]

I've noticed my engine sounds are changing when my rpm is above 2200 with cruise on. it sounds like it is slowing down and speeding up but, I've noticed no change in speed or change in rpm. seems to run fine, changed fuel filter, cleaned the k&n, still there... . any ideas?

 

[bud kohn]

no i was not running on defrost, and this was after engine was up to temp, so it did not have the voltage surge induced chande in sound as you do at idle with the grid heater going on and off. thanks fore the suggestion!

 

[Duluth Diesel]

The 24 valve engine have electronic variable timing, whereas the 12 valves have fixed timing (although it is adjustable). When the 24 valve computer adjusts timing (based on power demands, speed, and engine rpm) you will hear a different sound. The computer adjusts the 24 valve's timing constantly, and the change in sound is normal.

 

[JTroiano]

Vavle timing or injector pump timing?



Jon T

 

[Duluth Diesel]

Injector pump timing I think, but I may be wrong. There was a recent issue of TDR magazine that outlined the differences with the CTD throughout the model years, and in there the variable timing of the 24 valve engines was addressed.

 

[DMC]

You must want your motor to have a 1/4 life with that K&N on there. You should sample your oil at your next oil change. This way you can see the sand that is getting into your motor.



Sorry to seem blunt about the filter, but I have seen the oil analysis with the K&N on my own truck.



How many miles do you have on that truck with the K&N and total miles.



Don

 

[bud kohn]

Don, thanks for the input, I am not offended, I know the BHAF or OEM filter is the way to go.

My 2002 has abouth 75,000 about 15,000 with the K&N

my 1996 had about 325,000 all with a k&n when i sold it in 2000... it still is running at about 475,000. my 2000 had a replacement filter which did not meet OEM Requirements for filtration from what i read somewhere TDR? it ran for 125,000mi just fine.

I can live with 1/4 life of 1,000,000 miles

i don't think the filter is the problem, the funny sound was not there 2 months ago, maybe a louder exhaust, or a louder radio would cure my problem thank you to all for your input