2005 LLY problem; cough/hesistation thru intake?

[ccole]

Hello all..
Been a long time since posting, but lurk around just about everyday. I guess I havent posted since my LLY has been so trouble free and absolutely love it.
Anyway, my 2005 Chevy 2500HD with 8000 miles acted up the other day when I was pulling a 18' enclosed trailer. Not much of a load for a duramax. Anyway, when I was getting on interstate and accelerating pretty hard, my truck hesitated and coughed (almost sounded/felt like a old car back-firing thru the intake). It done it twice, one right after the other. I immediatly let off the throttle and eased back into it. It never done it again. The whole trip. Anybody have any ideas of what would cause this?
Some things to consider:
* loaded 18' stock trailer
* fuel filter has about 1500 miles on it (latest and greatest dual element racor filter)
* it was chilly on this particular day, but fuel should not been anywhere near gelling.
* no mods/chips

Thanks guys!

[tanker]

Outside of going to the dealer, I'd first change the fuel filter just to see if it changes anything. Although GM recomends 15,000 mile changes, you never know what you might pick up. It could be something else but without reading a code, I'd change the filter.
Let us know what you find. smile.gif

[Kennedy]

This sounds like a turbo bark. GM has a PI file on this. I wouldn't worry about it much. Sounds like there was a call for correction or the EGR simply activated.

Disabling the EGR system should cure this ;)

[ 12-29-2005, 06:49 PM: Message edited by: kennedy ]

[ckt]

Sounds a lot like the problem I have. There appears to be a bulletin on this, unfortunately there is no cure as of yet. Check my post on page 2, called "Noise at shift during hard acceleration". You can find the bulletin number etc.

[ccole]

Thanks for the replies. It is kind of a sigh of relief to read these replies! I was hoping that nobody would say that this was a pre-waring of the dreaded injector failure or something along that nature. I think I will go ahead a put a new fuel filter on, just to be safe. Thanks again!

[royalglen]

I have the same problem with "Back fire in engine" when accelerating or under load before engine not quite fully warmed up yet.Dealer had stock answer "nobody else is complaining" so live with it.It must be back fire in turbo area that causes it. Probably harmless???? Anyone with this problem should let service depts know so the volume of complaint will get answers.

[mark45678]

turbo bark.... My truck is one of the first few lly motors, its had it since it was new..... 70,000 miles on it now! 90% of those miles where juiced up :D so its hard to tell if its juice or ECM or EGR??? I think JK is right with his EGR statement. My truck sometimes would bark twice at the top of 3rd gear at full power. Not good for the crank and trans .

[ccole]

Yep... I agree 100% with you other guys on all your statements with this turbo bark situation. 1. Under hard acceleration. 2. When truck was not fully warmed up. 3. Usually on top side of 3rd gear.

I guess if its no big deal, I wont worry about it. (But I did go ahead and change the fuel filter, just in case).

Thank you for the helpful information.!!!!!!!!!

If I can return the favor by offering anybody a cut-rate on OEM John Deere Ag parts, let me know. I can help you out. Thanks again.

[markrinker]

At what RPM did this 'bark' occur?

[ccole]

It was hard acceleration. I would estimate around 2800 rpm. Thanks!

[bgruschy]

There is a buletin on this. Document ID# 1665614

I wish I knew how to post it...

[fire22dirver]

Where can I get a copy of the bulliten?

[ccole]

Not sure, other than asking the dealer for a copy of the bulletin. I contacted my dealer yesterday (because my truck done it again) and he verified that at this time, there is no solution for this problem. I guess we'll see what happens.

[Kennedy]

15904640 New calibration to address intake pop complaints

[mark45678]

I am not sure what the spec number is that they reloaded my truck with on Dec 23,2005 but it runs MUCH smoother , better power and it hasnt had a bark since then! about 2000 mile now, I could get it to bark almost any day the air was heavy and damp . Get the reflash you will not be sorry . smile.gif

[Kennedy]

This one was just recently released (days old) and at a glance, it appears that the maximum opening has been reduced to 15% wher before it was open as much as 50%.

No details on commanded opening changes yet...

[ccole]

Kennedy.... So are you suggesting on getting the newly released flash update from the dealer or hold tight for awhile?

Thank You....

[Kennedy]

It sure isn't going to hurt. The previously released 1100-1400RPM surge update comes with it but this is only altering (reducing) rail psi at a low pedal and the EGR thing can only be a good thing if it's reducing flow.

[ccole]

Thank You.

[ckt]

kennedy, do you feel the EGR changes and the lower rail psi will reduce power output? I would also like to thank you for all your posts. Having knowledgable contributors really make this site great.

[Kennedy]

No, the lower rail psi is way down at super light pedal. The area that you would use to creep through a parking lot.

The EGR reduction can only be a good thing...

[ccole]

Got the reflash update for the turbo pop from the area Chevy dealer. Knock on wood, seemed to correct the problem. Thank you for the info!