03 making noise at certain rpm

[JeffL]

Hey everyone, my 03 has been making a kind of ticking type sound at a certain rpm. Kinda hard to explain the sound but I'll do my best. The truck is normally fairly quiet, but the other day when I engaged the clutch to stop I heard the noise as the rpms were coming down to idle, just for a few seconds. It almost gets a louder "diesel" sound, almost like a Powerstroke sounds. I plowed all weekend and the noise has come and gone. When it's there, if I'm at idle and rev it up, as it comes back to idle it will make the noise, at around 1200 rpms. Thinking it may be an injector, sound logical? Had some hard cold starts a couple months back, but a fuel filter change and can of power service seemed to take care of it. Now again every once in awhile it's cranking a long time before firing. Definately sounds like a fuel knock, so I turned my smarty down to stock, which seemed to help at first but the noise came back. Any ideas? Thanks

 

[JeffL]

Also, I noticed tonight while plowing a drive that while I was going very slow the sound would start and the truck would almost pep up a bit. Almost like the timing is advancing, or something.
2003 3500 SRW 4x4 NV5600 Smarty AFE Stage II

 

[Prairie Dog]

Sounds like your FCA on the back of your CP3 is getting sticky. Not uncommon at that mileage and a pretty cheap fix too.

 

[JeffL]

Hmm, I replaced that a year ago, when I was having issues with the ECM. Could it go bad that quickly? What exactly would it be doing to make that noise? Thanks

 

[Prairie Dog]

Probably something else then. I take it there's no codes stored?

 

[JeffL]

Never mind, I didn't change that. I was confused with a different part. I will give that's try. Thanks

 

[JeffL]

I don't think there are any codes. No check engine light on or anything.

 

[JeffL]

Replace the fca with a modified one I had and the noise is still there. Does it make sense that it may be an injector?

 

[seafish]

The FCA can always be "diagnosed" by running up to 4 oz of two stroke oil in a full tank of diesel. If the noise goes away, then it the problem was a sticking FCA, if the noise remains then it is something else.

 

[JeffL]

Yeah, I replaced the fca, so that wasnt it. What kind of 2 stroke oil is recommended? Is it a good idea to run 2 stroke oil on a regular basis? I try to run power service as much as I can, but 2 stroke oil is probably cheaper and seems like it would really richer up the fuel. Do you guys think it could be an injector? Thanks