2012 Sierra tapping coming from motor?

[Scottergunner]

Hey guys I'm new here so thanks for taking a read. This past weekend I purchased a 2012 GMC Sierra with the 5.3 and I'm just now getting to drive it some and listen and it seems to have a irregular tapping noise come from the motor. At idle one minute you can hear it strong the next its quiet(er). Also at higher rpms in park it seems to smooth out. So the big question is, it this the infamous AfM bs taking its toll on a lifter? Piston slap? Any input should help. Thanks again

-Scott

[Jet-X]

I had a similar intermittent noise problem for 8+ years.  I attributed the noise to piston slap.  Turned out to be a broken exhaust manifold bolt. Check to see if you have any broken bolts. Driver's side rear is the most common.  

[MaverickZ71]

12 hours ago, Scottergunner said:

Hey guys I'm new here so thanks for taking a read. This past weekend I purchased a 2012 GMC Sierra with the 5.3 and I'm just now getting to drive it some and listen and it seems to have a irregular tapping noise come from the motor. At idle one minute you can hear it strong the next its quiet(er). Also at higher rpms in park it seems to smooth out. So the big question is, it this the infamous AfM bs taking its toll on a lifter? Piston slap? Any input should help. Thanks again

-Scott

If it does it only at startup, it's probably AFM lifter(s).  The 2007-2013 generation is not known for the GM piston slap, but it can happen. 

 

The consensus on here is to turn off AFM as soon as you can via a Range V8 module or other PCM tune such as Hypertech, Diablo, or BlackBear.  Most people don't notice a significant change in fuel mileage with AFM off.  And to mitigate any potential AFM problems, be sure you use quality Dexos rated (synthetic) motor oil such as the new Shell Gas Truck oil and freer-flowing oil filter, and change it every 4K miles or so, regardless of what the Oil Life Indicator in the Driver Info Center display says.  

 

The problem is that a bad lifter can turn sideways in its bore and scar the camshaft.  If it comes to that, then you'll probably want to do an engine rebuild with an AFM delete kit from Texas Speed.  

[Scottergunner]

I purchased a programmer yesterday to turn the afm off. And it's just not right after start up it's always there. And there noise comes and goes

 

 

[diyer2]

If it was me I would do an engine flush with a product of your choice.

Easy, cheap.

Some oil passages for the AFM maybe plugged or partially plugged up.

I use Sea Foam for this.

 

[Scottergunner]

6 minutes ago, diyer2 said:

If it was me I would do an engine flush with a product of your choice.

Easy, cheap.

Some oil passages for the AFM maybe plugged or partially plugged up.

I use Sea Foam for this.

 

Yeah I'm probably going to change the oil for the heck of it this weekend to see if that will shut her up

 

[diyer2]

Perfect time to add a flush chemical to oil before changing it.

 

 

[Scottergunner]

3 hours ago, Jet-X said:

I had a similar intermittent noise problem for 8+ years.  I attributed the noise to piston slap.  Turned out to be a broken exhaust manifold bolt. Check to see if you have any broken bolts. Driver's side rear is the most common.  

Unfortunatly I just check this and it doesnt seem to be that

[Mikebtte]

Check your rocker arms as its simple and sometimes the bearings come apart and send needle bearings to your pan. Worth a look.