"clatter/cackle" off idle

[GLolas]

Do you guys have a "clatter or cackle" right off idle? I seem to have it from idle to about 1000-1100 RPM when I'm accelerating slowly. Once I get above 1100 RPM its gone and its nice smooth grunt power and sound. Its an SO with a 47RE. I'm still learning so bear with me. Thanks

 

[lschultz]

What did you drive before this a dord?No I have not ever heard this. You are in the right place to learn about Dodge/Cummins.

 

[David Muench]

Happens to me all the time. It seems to depend on a lot - how hard you push the accellerator, temperature, etc. It's just the pilot injection going on/off.

 

[GLolas]

Dave, It does depend on how hard I accelerate and how warm the engine is.



Ishultz, Never owned or driven one. Always Dodge products, but this is my first CTD.

 

[David Muench]

Get it up to a high RPM, and it'll do it also. The pilot injection turns off then because it only can do it up to a certain RPM. I have no idea why it comes and goes at low rpm's starting off, but I'm sure it has a reason.

 

[rogerblind]

My HO 6-speed does the same thing. I was wondering what it was. It sounds about like my 2002, until I get up a little rpm. A question. If it is the pilot injection going on and off, when is it noisy ... when it is off or on?? I would guess off.

 

[krabman]

Some of this stuff is pretty interesting cause mine does this only when its dead cold and at any RPM. As soon as I go down the road for a few minutes it stops and does not do it any more at any RPM. Weird how people will have the same thing going on with their trucks but it will manifest itself in different ways.

 

[PCline]

I've noticed that mine only does it when there is no load on the engine (and it's cold).



If I coast for a bit and then ease the throttle back on it'll be loud just until the engine to picks up the load.



Seems like the pilot injection only keeps things quite if there's a "preload" on the engine components. Kinda makes sense as the pilot injection is intended to smooth out the pressure wave. Without a load the engine components have more "freeplay" to rattle around in. Even a smooth pressure wave would cause some rattle.

 

[91W350]

If I follow you correctly, mine is doing it also. It is a cold rattle with mine though. Usually within a half mile it has quit. I suspect a combination of sensors coming up to operating temperature are the culprits. I never let mine idle cold though, just drive it really gently until the engine is warm enough for the oil pressure to drop. This truck has turned out to be my favorite vehicle!

 

[coonrod70]

Rattle

I have also noticed this on my truck with 2000 miles on it. Seems like it only happens when cold. As this is my first diesel I chalked it up to being a normal cold weather thing. As for not letting it idle when cold, this don't seem like a good idea to me. I can understand not idling for long periods of time , but for a minute or two seems like would be good to let the fluids circulate and warm a bit before taking off down the road, even if your driving slow.

 

[David Muench]

It clatters when the pilot injection is off, the pilot injection is designed to quiet the engine down.

 

[91W350]

I agree in extremely cold weather, it would be good to let it warm up some, mainly because I hate scraping windows. Even then I hold mine above a low idle. I do not know about the rest of you guys, but when the temperature is below 20 degrees, mine might go ten miles before getting warm enough for the operating temperature to reach normal levels. I doubt letting it idle for ten minutes would warm the transmission any noticeable amount. I would think that due to the high compression ratio, Cummins would run a forged piston. Driving hard on a cold forged piston would be inviting trouble as the piston does not expand at the same rate as the cylinder block. I still think driving easy at least until the oil pressure drops to normal pressure is the best plan. Does anybody here jack up their truck and spin the differential to warm it and the transfer case up before driving in cold weather? I have yet to plug mine block heater in, but I hear that makes the world wonderful in the cold! Just curious how far we go towards warming fluids. In the days of old, Caterpillar guys built fires under the Cats to keep them warm or warm them up enough to start. They claimed operation with warm case oil was a lot nicer too. I do not think I'll be building any fires under my Dodge!

 

[rbattelle]

This rattle/knocking that you guys describe is interesting. I experience the same sort of thing, but it comes and goes. I find it most prevalent at extremely light throttle and low RPM (900-1100). I actually don't notice it so much when it's cold, but I think that's because the engine is noisier when cold so it's masked a bit. When the engine is fully warmed, that's when I notice it when starting from a stop or at very light throttle at speed.



I hope it is just the pilot injection turning on and off.

 

[91W350]

I have a 1985 Chevrolet ex-military 6. 2 4X4 5/4 ton. After driving it, my Dodge has no rattles! Anyway, the old Chevy really bangs and rattles, even when warm. It is the worst in the really low rpm ranges though, just of idle. My Dodge is the loudest there also. I suspect in both cases, the engine is not very efficient in that rpm range. A buddy's Powerstroke is the same way. I do not recall if the big Cummins truck engines have that low rpm rattle, that's hard to believe after thousands of miles in a big rig, I guess it was somebody else's problem. I think the low rattle is just the nature of the diesel beast.

 

[RSnaith]

Originally posted by rbattelle

I hope it is just the pilot injection turning on and off.

This is indeed what you are experiencing. The pilot injection can turn off from time to time. We haven't found a reason or an explanation for it, however it is occuring under a certain set of sensor values, and even occasionally as you are driving down the road.



Rod

 

[CATCRACKER]

maxi do it with thier pilot injection also nothing to worry about. all of the 03's do it.

 

[rbattelle]

I think the pilot injection turns off when you're below peak torque RPM (1400) and under load (such as when starting from a dead stop). But mine does it only when warm... when it's cold it seems to retain pilot injection throughout the RPM band.

 

[rbattelle]

Another Observation

This knocking noise with pilot injection off is fascinating. I've noticed it tends to go away sometimes for several days, then suddenly start happening again. I've tried to relate it to ambient temperature, but I'm not convinced it is.

 

[Rosco]

rbattelle, I agree with you. It seems that some day's my truck knocks/rattles more than others. Oh well, if other truck are doing it I won't lose sleep over it.

 

[Shooter]

Mine does it first 1/4 - 1/2 mi, when cold. I can only hear it with window down. Kinda sounds like my 00 did all the time. It does not do it any other time. Only lugged it once ( wrong gear ) BOY was that a sound I never want to hear again :--)