2011 6.0 Engine Knock

[Portdriver]

I have a 2011 2500HD w/6.0 that has a slight engine knock while under light acceleration. It does it warm or cold. I switched from 87 to 89 octane a few months ago and this semmed to help. Today I noticed it again. I'm off tomorrow so guess were I'll be spending my day off? at the dealer. Any one else having this problem? Anything I need to know before going to the dealer? Thanks!

[Stephenspann27]

I have this problem on a 2002 5.3. I have verified my fuel pressure.. run seafoam through it.. nothing has helped so far. Mine is worse when it is hot outside. Like you, I think premium seems to help a bit.. but I spend enough on gas as it is. I also get pinging (knock) at WOT for a few seconds. If your dealer is able to fix yours.. please report back what they changed.

Thanks

[govtech]

^{no there is nothing you need to know before taking it in ,}

 

^{just road test it with a svc mgr or advisor or shop foreman,that way they cannot say "no fault found " after you say "that noise there" during the road test}

[Doug_Scott]

I would imagine you are getting very poor mileage as well. Assuming they still have knock sensors, your engine should be at max retard timing. Shouldn't that throw a CEL?

[TJay74]

I would imagine you are getting very poor mileage as well. Assuming they still have knock sensors, your engine should be at max retard timing. Shouldn't that throw a CEL?

 

 

Nope, wont throw one code at all. The SES light will flash if a misfire is detected. There are 2 different timing map profiles in the calibration. There is a high octane map and a low octane map. If there is enough detonation recorded for a long enough time (this is called an EVENT) the ECM will drop down into the low octane map until enough decay time has elapsed then will come back up into the high octane map.

 

I get some piston slap until the motor warms up. Only way to see if this is detonation and not piston slap would be to find a shop that can scan the vehicle while it is driving. I have HP Tuners I use on my vehicles so I can scan real time and see exactly what the vehicle is doing.

[Portdriver]

 

I'm getting 9 - 10 mpg around town, 15 - 16 highway - with 275/70/18 Duratrac tires. I drive mostly city/suburbs. I had a few people tell me that they all have a little piston slap but from my reading on the forums thats not the newer trucks and only when cold. Can I hear a difference between piston slap and detonation? Any way for me to tell the difference without a reader?

[TJay74]

Piston slap tends to go away once the motor warms up, detonation can be heard when driving and under load.

[Portdriver]

 

 

Piston slap tends to go away once the motor warms up, detonation can be heard when driving and under load.

Then it's detonation. Thanks TJ. Just got in from the dealer - NTF - no trouble found. The tech couldn't hear it when he drove the truck then I drove it and he could hear it. He said he checked everything - normal operating parameters - no codes. Checked with GM and told me to try changing type/brand of gasoline. I'll change brands but I'm running 89 now. If it's still pinging in a month back to the dealer I guess. I do not think its normal. At least it's documented if there's any more problems.

[Stephenspann27]

I've been told that it says somewhere in my owners manual (I have a GMT800) that pinging is normal. Of course.. no one wants to accept that..

[TJay74]

Depending on miles it is possible the valves have carbon deposits on them which would offer potential hot spots with in the combustion chamber and could cause detonation.

 

In esscense detonation is when there is a hot spot in the combustion chamber. When the fuel is injected in and the piston rises to compress the mixture the hot spot is hot enough to ignite the fuel/air mixture before the spark plug ignites the mixture. In turn you have two flame fronts that end up colliding with each other, that collission is the "pinging" we hear and under severe enough circumstances is akin to taking a ball pean hammer and hitting the top of the piston.

[Stephenspann27]

I would think his truck is far too new to have that problem. Mine is old enough for carbon to be an issue, and that's why I have seafoamed it a few times. However, timing that is advanced too far can also cause pinging. Higher combustion temperatures contribute to this.. a malfunctioning EGR etc. I highly suspect that mine is a timing issue. For a week or more I was running with bad knock sensors (washed my engine) and when the engine was running its "safe map" I had no pinging.

[Portdriver]

 

The truck has 4400 miles on it. I first noticed it around 1000 miles. I then switched to 89 gas. That helped but didn't resolve it. The manual says it can run on 87 or higher. Is the "or higher" part GM covering their ass? At about $42,000 sticker price I want it right.

[anthony2558]

I have '12 2500HD 6.0L and have noticed the same issue. I've gone through 6 tanks of gas all from different places and a bottle of lucas fuel system treatment with no help. Mine is always noticeable under low rpm when the engine seems like it wants to bog, as if the fuel is not combusting correctly. Detenation seems to be the correct word to describe what im experiencig. Has anyone resolved this problem. Thanks.

[HEMICAT]

My '12 does not have this issue. Now I will be paranoid listening while I drive! Same thing with the other thread about rear end shaking-mine doesn't, but I am always checking to make sure.

[Portdriver]

Still does it. Dealer says normal or run different / higher octane gas. I sent a sample of engine oil to Blackstone last change. They said copper was high but normal for the engine/miles. Should be better next time. It's all documented. Still DO NOT want to accept that its normal.