Cold Start Hesitation

[11/SS/RS]

Hi Everyone, so I have my SS with 6.2 L99 Ive noticed from the time I got it, when you cold start it, It she fires right off, goes to high idle then drops a bit, like a stumble, then goes to a normal idle... Its never failed me and seems just fine for every start after that.... Has a K&N CAI and a cat back...

Now, I just bought a 2012 Silverado 1500 with a 6.2... It has a Banks CAI & a Pypes cat back... It starts the exact same way as my SS... BUT, its a more severe stumble after is goes to high idle when first started. It stalled on me one time, but every other morning, it stumbles hard.

This is ONLY the very first start of the day.. Im trying to figure out if this is a normal trait of a 6.2 of the era, or is something else going on... After some research, there are quite a few people with the same issue on the Silverado, but never a definitive fix for it.

Both engines are in excellent condition, no issues and otherwise run excellent... Ive tried Techron, BG 44K, new MAF, cleaning the throttle body, Fuel PSI is 60+ KOEO, 44 psi running, changed fuel stations always 91 octane.... nothing is really making a difference. No codes, and everything seems normal otherwise.

Any ideas?
TIA

[Aqua Blue RS/SS]

Both my L99 Camaros have done it as does my wife’s ‘11 6.2 powered Yukon Denali. It’s a bit annoying trying to get the Camaro out of the garage real close to the garage door opening while it’s bucking like a mule.

[FasNuf]

Possible transiitioning from open loop to closed loop based on coolant temp?