2015 Sierra 5.3 Bad Idle and Rattle sound from ????

[Cvincent]

Hello all, I am new here and yesterday I posted some questions that I really need help with in 2 locations because I didn't know where to post them correctly. Consequently, I never got any answers maybe because the admin deleted them both. My bad, I honestly didn't know where the right place was. So here are a couple of my primary concerns with this truck, if anyone can help I would appreciate it...

 

The dealer had my truck for 6 days to replace a broken dash piece and to troubleshoot driving issues. During the test drive, the service (manager?) stomped the gas to the floor and we both heard a metallic sound, he repeated it numerous times and the sound always came back. To me it sounded like a couple of lifters that were about to shoot out from under the hood. We went back to the dealership where I was asked to wait while he and the shop foreman went for a drive. When they returned I was told that it was "just and exhaust noise" and it was "perfectly normal".

 

They insisted I take a drive with the shop foreman even though we all agreed that I feel issues that they believe to be normal for this vehicle, so the test drive was pointless. Nonetheless, we drove. I showed how when I step on the gas to take off the engine seems to bog down and lack throttle response, I also showed how at each and every stop the truck shakes like it is having an epileptic fit. The explanation I got was that this was the active fuel management system just doing its job and it was "perfectly normal".

 

Call me crazy but I just can't wrap my head around a new vehicle of any type, but especially not a 54K vehicle shaking like crazy, rattling under heavy throttle and lacking the power to get out of its own way to be "perfectly normal".

 

But maybe I am wrong, any thoughts or advice would be super appreciated.

Thanks

[HawkeyeSierra]

I'm no mechanic, but the things you're describing don't sound normal. I've also got a '15 Sierra with 5.3 and it's smooth as butter.

[20SierraL8T24]

Keep on em and don't settle for their so called "normal". Good luck buddy

[Cvincent]

thanks guys, that is the plan.

[HondaHawkGT]

Well if something mechanical is knocking, the knock sensors might pick it up and pull timing. It would definitely make the truck feel weak or lethargic.

 

AFM shouldn't have anything to do with the engine when you take off from a stop. Sounds like a tech needs to take a closer look at the truck. Unfortunately all manufacturers instruct service departments to check for codes and if nothing comes up, they deem it "normal".