I recently bought a new '05 LLY and I've got about 1600 miles on it now. Since day-one it has had a pinging or knocking which is quite obvious. This occurs most at low RPM, from idle up to about 1800, especially on deceleration. Sounds like an ignition ping.

I've been around several new '05 LLYs and only noticed this noise on one or two others, so something must be different. Most of them don't sound like this, so what's causing it?

I've seen similar issues raised on this forum in the past, but without much of a resolution. I'm wondering whether anyone has figured it out yet.
Most of the previous descriptions seem to be at higher RPM or under load. Mine does it most at low RPM, all the way down to idle, and is most apparent while decelerating, although it's there during acceleration too.

I've asked the diesel tech at our dealership as well as a couple Duramax friends, but no one really has a good idea. Does anyone here have one?
Why do some of these LLYs do this while most of them don't?

Thanks,
Tony

I believe it is a pin that has not found its seat yet. This may not be entirely correct because I can't hear your ping. The cure is to just drive it. It should quiet down after several miles. Unless it is something that makes you say "This thing is going to come apart", I would not worry about it. 5 year, 100,000 mile warrenty, if it is an issue, you should know by then. You can do a search about this, there is several threads about this. Congrats on your purchase!

You know you may want to post this over in the ask the techs section, pinging sounds like injector or injector timing issue to me... especially pinging while decelerating.

if its the same sound I think you are talking about..its the pilot injection you are hearing. try a search on that and see what you come up with. most of them do that, but depending on what mods if any, it may be louder on some than others.

I am familiar with the pilot injection (or lack thereof) noise that occurs around 2500 rpm or so. My truck makes that noise like they all do, but that's not what I'm talking about. Like I said, it's most apparent at low rpms, especially during deceleration.

What else it is not is that infamous ticking that some folks notice. My dad's DMax does that noticeably, but that is a less obvious sound. It also is intermittent, where as mine is totally rythmic with the engine speed.

Someone said to me a few days ago that it sounds like a rocker arm knocking. I thought to myself then that it actually reminds me of a gas engine that's almost out of oil, when you can hear the pushrods knocking on the rockers.

What gets me though is that I have heard at least one other '05 LLY make the same noise, so it's not totally unique to mine. I've got about 2,000 miles on it now and there's no reduction in the noise.

I don't know, guess I'd describe it as halfway between a typical ping and a knock. It's aggravating at best, and a problem at worst. Have I described this well enough for someone else to realize he's experiencing the same thing?

Tony

do you have any way (i.e. Predator) to check your balance rates? You'd be surprised at what a fuel knock sound will imitate on a diesel...

I have the same sound I only hear it on deceleration also.I mainly hear it from like 20mph coming to a stop,but I dont hear it once completley stopped but I do hear a single click every couple of revolutions at an idle. A buddy told me it was the EGR so I unplugged it and Im still hearing that annoying clicking

Someone gave me an idea that might be the answer to what's going on here and/or how to fix it.
I was thinking about the only other LLY that I have heard make a similar noise. It was Steve's (GrayMax) first dually truck after we changed the ECM. It didn't make the noise before changing the ECM.
Apparently there has been an issue discovered by GM that occurs occaisionally relating to the fuel injector flow rates.
When each injector is made, it is flow tested and marked as to what its flow rate it. This information is supposed to be stored in the FICM and downloaded to the ECM. In some cases when ECMs have been changed, the injector flow rates are not downloaded to it, and therefore it runs based on a standard indexed flow rate instead of custom ones. This issue was brought up at a Duramax training session in Las Vegas recently. They said that symptoms can include poor fuel economy, smoke, and combustion noise, based on how far off the standard calibration is and in which direction.

The ECM in my truck has not been changed since I bought it, but perhaps it was changed at the factory for some reason.
The noise, I've decided, is definately some kind of combustion noise. The rhythm is slow enough that you can count them individually; they occur maybe 4-5 times per second.
Just figuring in my head, an engine running at 600 rpm turns 10 rev per second. A V8 engine fires 4 times per revolution, or 40 times per second at 600 rpm. If only one cylinder is doing this, then that would be 5 times per second, which happens to be about the frequency of the noise at an idle. So I'm thinking maybe I'm onto something...

Supposedly you can use a Tech2 to go into the FICM and activate an injector flow rate download to the ECM. This is what I want to try to see if it fixes it. I've just got to get some time to get someone with a Tech2 to help me with it.

Has anyone else heard of the issue from this perspective? Does my thinking sound about right?

Tony

I have complalined about this noise from day one over a year ago. The dealer said it is normal. KB made some points in This (http://www.dieselplace.com/forum/showthread.php?t=38802&page=16)thread which I think relates directly to this sound. It has got me wondering if the ping is related to what is causing the overheat....................

you have pilot injection rattle. ask your dealer for bulletin PIP3301. it explains it quite clearly.my 05 does the same thing. i added power service cetane boost to the fuel and it eliminated 70-80% of the "RATTLE". hope this helps. Courtney

I did have this ping sound too on my 05 GMC D/A, but it is completely gone now! I know when it stoped too. I had to pull our cattle trailer from TN to AR (900 miles round trip) about two months ago. This was the first long pull for the truck other than about 50 miles to the stock barn every two weeks or so. I notice the ping mostly when I was filling up, and on the way back at a Pilot I noticed it was not pinging anymore, and has not pinged since. Maybe just take a good long pull, after all thats why we bought them right?

Thanks,
Anthony
05 GMC 2500HD D/A 4x4 CrewCab

you have pilot injection rattle. ask your dealer for bulletin PIP3301. it explains it quite clearly.my 05 does the same thing. i added power service cetane boost to the fuel and it eliminated 70-80% of the "RATTLE". hope this helps. Courtney

I don't think this is it either. The bulletin that you mention states:

"Engine timing burst rattle at 1500 -1800 RPM (light acceleration, light load fully warm). Compare timing burst rattle to a like 6.6L LLY Duramax Diesel engine. For the "04" model year LLY engine, verify the vehicle has the updated ECM calibration for Engine Combustion knock. For diagnostic purposes advise using 1 - 2 tankfuls of a name brand / different source of diesel fuel to determine if the concern is caused by a fuel quality issue."

The ping/tick/whatever is not only at low rpm. You can hear it at any rpm, from idle to redline. Also, they say compare to a like LLY. I've heard plenty of other LLYs run, and have only heard this noise on one other one. Even then I'm not sure it's the same noise, because I heard it on that truck before I bought this truck. For sure, most LLYs do not make this noise.

I don't know what to do about it, but I've got 6200 miles on it and it does definitely aggravate me. Even though I don't think this "timing burst rattle" is what I'm talking about, I might still want to try what you did with the additive. Is it a long term fix or do you have to put it in the tank on every fill-up?

And you know, if that were to help the problem, I'd still be aggravated because I want to know what it different about mine from all the rest that made it do it to begin with, and I cannot figure that out. Methinks it's got to be some kind of injection issue, either an injector itself or calibration...

Tony

tony, iadd about 10-16 oz per fill up. 30-36 gal..ifind there is a difference in fuel . my 05 is quieter using citgo verses exxon..the noise is apain, icall it anuisance noise, may not hurt anything ,but its a distraction.can't hear it with the windows down. take care courtney