Sounds like low octane gas knock

[C130guy]

New to this forum, drive a 2014 Sierra Crew Cab 5.3.  Since owning the truck, on acceleration I hear what sounds like the old days bad gas / low octane rattle?  I've run tanks of 87, 89 & 93 octane and it's always there.  I even tried a tank of ethanol free gas and it still  rattles on acceleration.  For those that suggest searching the hundreds of threads....I did, couldn't find what I was looking for, figured it would just be easier to ask.  I did learn a lot about flapper valves and drone noises.  Any help would be great, dealership said they don't hear anything that sounds like what I'm describing....imagine that.  Thanks for the help / info.

 

Scotty

[kstruckcountry]

Is it possible you're hearing the injection system?

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[diyer2]

32 minutes ago, kstruckcountry said:

Is it possible you're hearing the injection system?

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This is my guess. Higher octane fuel didn't help, right?

[Grumpy Bear]

I three peat that. Took me awhile to get use to the direct cylinder injections rattle. Anymore I only notice it when I have the window down. 

[C130guy]

@Diyer2.....all octane levels give the rattle.  Leaving work today, radio off, windows up.....I got on it and she was a rattling until I come off the pedal.....if it's the injectors I guess there isn't much you can do.....accept a Cat Back exhaust system!!!  That's what I'm reading up on now   Thanks for the replies.

[Scuba78]

mine did this too...just fixed it with the help of Blackbear Performance.  GM runs these truck really lean.

[wmgeorge64]

Lean used to mean engine running hot, burnt valves and perhaps piston damage.  Does that still apply with high pressure direct injection engines. with high compression ratio?

 

[Scuba78]

not sure how that holds true, but they seem to tune it to the point it barely uses fuels instead of using a bit more for better drivability and lubrication

[Bassinz71]

Had something very similar on my '14. It was at the dealer 5-6 times for it and had two of the GM chemical cleans. Eventually went on a ride along with the mechanic while he had his computer hooked up. Had a few misfires that he saw but suggested the rattle noise was from the valves being dirty and I needed to burn them off. Also suggested a catch can. 

 

I put the can on and began to run the truck harder (hotter) and after 6 months or so I get very little of the rattle. 

 

The mechanic is a local tuner/engine builder and seemed to know his stuff so I took his advice and it paid off. Hope this helps.