Vibration Idle

[Whofartedwasntme]

Picked up a 2016 LTZ 4WD 5.3L 6spd trans with about 113k on the clock. Once engine reach’s op temp, it as a slight random vibration/shudder sitting still at idle when in Drive, less frequent in park. Nothing crazy, but just enough to annoy me lol. i don’t notice anything when moving. I changed the oil, plugs and coil wires, did the transmission filter/fluid change, changed diff fluids, put in the Range AFM delete, ran some BG44k, and cleaned the throttle body (didn’t remove). Seems a little better but might just be in my head. Anywhere else I should look? No codes or anything.

New to Tahoe’s but have a lot of wrenching experience with older Land Rovers, which appear less finicky than these hoes.

 

[Marky Dissod]

Check engine mounts.

 

[Whofartedwasntme]

Check engine mounts.

Thanks man. Can they be tightened? Wasn’t sure if that is DIY or need a prof

 

[Marky Dissod]

Thanks man. Can they be tightened? Wasn’t sure if that is DIY or need a prof

Correctly installed, it's unlikely they need re-tightening. It's far more likely they've aged past retirement -
their job is to minimize engine rock absorb NVH before your significant other tries to convince you to buy a different vehicle that is less annoying,
but the nature of that job is such that no motor mount can last forever; although 113k miles would indicate that they've aged ... very quickly / prematurely.

That you don't notice anything when moving tells me the next place you ought to look is the suspension / steering / brakes.

 

[Whofartedwasntme]

Thanks for the feedback. I don’t think it’s motor mounts bc it only happens in drive. In neutral/park no issues. Took out the throttle body and thoroughly cleaned it. Driving me nuts. RPMs hold steady but I can feel a little jitter when sitting still in Drive. No other performance issues noted. Changed the air filter to factory as well.

 

[Whofartedwasntme]

Is it possible coil packs need replacement?

 

[Marky Dissod]

Changed the air filter to factory as well.

So long as the MAF is CLEAN, this means nothing (although some air filters are not as good at fine particle filtration as others).
ANYWAY

Is it possible coil packs need replacement?

Unlikely. More likely is that one or more of your fuel injectors need CLEANING - don't rush to replace them too soon.
Very seriously consider double dosing on a Fuel System Cleaner that contains Poly Ether Amines; do your research.
I typically run 2 full bottles of Chevron with TechRon Fuel System cleaner in a full tank (of E85 'cause I can) and get leadfooted before the oil & filter change.

 

[Whofartedwasntme]

I’ll give it a shot thanks

 

[Whofartedwasntme]

I did clean the MAF fwiw

 

[Rygrego]

Throttle body cleaning. I would recommend removing the unit and clean with throttle body spray and a toothbrush. And as stated before a fuel system as well as an induction system cleaning .

 

[Rygrego]

Is it possible coil packs need replacement?

If you don't have a scan tool you will waste a ton of money shooting the parts cannon. A scan tool will tell you if you have a cylinder missing or a fuel system issue.

 

[Marky Dissod]

Is it possible coil packs need replacement?

Stop firing the parts cannon at the ignition system.

 

[Whofartedwasntme]

Stop firing the parts cannon at the ignition system.

Just doing general overdue maintenance. Was hoping to resolve it along the way

 

[Whofartedwasntme]

Throttle body cleaning. I would recommend removing the unit and clean with throttle body spray and a toothbrush. And as stated before a fuel system as well as an induction system cleaning .

Did it 100% clean last night. No luck

 

[Too_L8T]

my moneys on motor mounts

 

[MrTris]

All good things to check, but, in my experience, that idle shake goes away after a solid cruise - how often and for how long are you driving it?

I just returned from a road trip and at destination, in-town idling at lights, and while parked, the shakes I had previously experienced were significantly mitigated. I've never been in a GM truck that didn't have at least a little shiver at idle, so, I presume it's normal, but, all the same - get out and give it some room to stretch its legs. It's like it's saying, "C'mon, dad, let's GO!"