[RGoose]

I've done a bit of searching and can't find the answer. I have a 2006 2500 and when I lift off the throttle (after revving the engine or just holding the throttle steady as when driving) my engine does this stuttering thing (doesn't sound like turbo bark). The revs bounce a few times then settle out.

This is my first diesel, but I know this isn't normal. The truck is stock (as far as I know) which the exception of a 5" turbo back exhaust with FTE resonator. I've included a link to a short you Tube video that illustrates the issue. Any ideas? Let me know if you need better video of the problem (I just used my iPhone this morning).

Thanks,
Rob

Cummins Stutter.MOV - YouTube

 

[gordy michael]

so in the video you only pushed the throttle once?

 

[RGoose]

so in the video you only pushed the throttle once?

No, I hit the throttle a total of 4 times, it's immediately after I let off the throttle where the problem is. If you turn up the volume (it's a little hard to hear in the video) you can hear it best after the second time I rev the motor. It is much more noticeable in person than in the video.

Rob

 

[gordy michael]

Can you post a video of just doing it once?

 

[RGoose]

OK, after a big delay and several really bad attempts at trying to capture the "stutter" with a single rev, I have the following (Note, turn your volume way UP in order to hear the "stutter"):

One Rev Stutter

Any input appreciated!

 

[steelhead01]

it's called CUMMINS LAG, takes some time to get all that cast iron spinning up. The revolving reciprocating parts in a 5.9 weigh as much as a whole engine in some small imports. Dodge also has routines in the software to protect the engine/drivetrain from op. FU such as overrevvling in neutral.

Your main malfunction trying to diagnose a normal condition.
these do not respond nor sound like a gasser

"""This is my first diesel, but I know this isn't normal."""""

get a CD of a gasser hot rod and play it loud in your truck, you'll feel right at home

 

[cerberusiam]

Perfectly normal with HPCR system. Lifting off the throttle does not immediately drop rail pressure so the rpms are stepped down as the fuel delivery is stepped down.

No throttle plate to chop air flow. Rpm's are purely fuel controlled and the system is protecting itself from pressure spikes.

 

[RGoose]

it's called CUMMINS LAG, takes some time to get all that cast iron spinning up. The revolving reciprocating parts in a 5.9 weigh as much as a whole engine in some small imports. Dodge also has routines in the software to protect the engine/drivetrain from op. FU such as overrevvling in neutral.

Your main malfunction trying to diagnose a normal condition.
these do not respond nor sound like a gasser

"""This is my first diesel, but I know this isn't normal."""""

get a CD of a gasser hot rod and play it loud in your truck, you'll feel right at home

I think we're talking about two different things. I'm very familiar with turbo lag as I used to drive a 1987 Porsche 930 (there are guys who hit the gas in the 80's and are STILL waiting for their turbo to spool up).

What I'm referring to is what happens after I let off the throttle. The revs drop a little, "bounce" up and down a bit (2 or 3 times, very subtle in the videos, more obvious in person), and then returns to steady idle.

After the throttle is released the heavy reciprocating mass of the engine should result in an engine that returns to an idle condition slowly but smoothly (due to inertial motion), not cause it to stutter or bounce. It also happens when driving (it's actually more pronounced just harder for me to get good video ), but only when I give it a little bit of throttle and quickly let off. It's as if the engine is getting a couple of small pulses of fuel after I let off the throttle. I hope that clarifies the issue.

 

[steelhead01]

HPCR rail pressure hysterisis.
takes awhile for the injectors at idle to bleed off RP from a high "goosed" rpm level.

get a high quality digital high resolution RP gauge on it and you will see correlation between RP and rpm change

recording rapid RPM changes vs RP is even more informational

also gasser indirect injection is MUCH different than direct injection gas or especially DI diesel with both injection pressure and duration changing per ECM command. The FCA in a HPCR is a slow mechanical device in a HS digital loop system

 

[superman279]

I had a similar problem, had leaking injectors. The stutter occurred when the engine returned to idle from >2500 RPMs. Your video was only 4 seconds and it was when you bump the throttle, your issue might be different from mine.

 

[RGoose]

Perfectly normal with HPCR system. Lifting off the throttle does not immediately drop rail pressure so the rpms are stepped down as the fuel delivery is stepped down.

HPCR rail pressure hysterisis.
takes awhile for the injectors at idle to bleed off RP from a high "goosed" rpm

OK, now that does make a little more sense. I just don't see it happen in other videos I see with people revving the hell out of their trucks. That's what made me think what mine was doing was not right.

 

[06 5.9]

to me it sounded like a loss of pressure in the first video.... no expert just thought thats what i heard

 

[06speed]

I have seen and heard an 06 that does this.

That being said,

MY 06 has NEVER done this. I have been through a couple of OEM reflashes, as well as current bullydog programming. Never once.

 

[Silver70]

Mine does it, I think it is called rail hang. Not sure if this is the case. Mine usually does it in first gear and the shift to second.