Brand new truck sputtering on start up

Svenleven · July 22, 2012

Hey guys,

I did a quick google search without much luck, so I thought I'd ask here to see if anyone had any thoughts.

I've got a 2012 Sierra Denali (with the 6.2L) and for the last 6 weeks or so on start up it just sputters and chokes for about 10 seconds before the RPMS normalize and then it runs fine. It only does this after sitting for a while (i.e. over night or for a few days), and once its been running that day it will start normally. Today when I started it, it actually sputtered and died until I restarted it and gave it a little shot of gas, then running perfectly after that again.

I'm hesitant to bring it to the dealership since they will likely just start it up, have it run fine and do nothing since it may take a couple of days for it to happen again.

I always run premium (91 octane) and very rarely let the gas tank run low.

Fuel injection issue maybe?

Any ideas would be much appreciated. Thanks in advance.

MikeNH · July 22, 2012

Mine has sat for a week several times and fired right up without issue. I'd get it to the dealership, something is obviously amiss. Do you always use the same gas station? If so, run this tank out and try another station maybe? Any modifications?

Svenleven · July 22, 2012

I go to a few different gas stations, but always "name brand" ones. Almost always either Shell or Petro-Can. (I'm in Alberta).

Also, no modifications.

BlackZ71Silverado · July 22, 2012

I had that cold start sputter when I was running the POS Volant CAI. Ended up being a vacuum issue. Check and make sure the breather hose is attached to your air intake properly and nothing else is leaking/loose.

Mikeb52r · July 23, 2012

Take it to the dealer, it is a warrenty item so its their problem. Let them fix it, also they probably will need to keep overnight since you said its only on the first start of the day. Even if they don't fix it, you have it documented for later.

SouthCo · July 23, 2012

Take it to the dealer, it is a warrenty item so its their problem. Let them fix it, also they probably will need to keep overnight since you said its only on the first start of the day. Even if they don't fix it, you have it documented for later.

X2... Yeah I'd take it in if only to get it documented. Mine has sat for a week at times and always started right up.

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waumo1 · July 23, 2012

It is a warranty issue but you might try turning the key to run (not start) 2 or 3 times for about 2 seconds before you then start it and see if there is a difference. If so, it might be the fuel pump. On my last truck, you could hear the fuel pump run for 2 seconds when you turned the key to run. I'm not sure if the new ones do the same.

Svenleven · July 25, 2012

Hey thanks to everyone for the replies. I wound up bringing it in and am waiting to hear back on what the issue might be. I was leaving town for a week so I told them they could have it for then and use the time to figure out what's wrong. I'll try to post the results once I know in case anyone else runs into a similar issue, but hopefully this is just kind of a one off deal.

Svenleven · July 26, 2012

So I got a call this morning, they did experience the rough start, but have no idea what it is. The best advice they could come up with was to try not using Shell gas "because of all the additives and see if that fixes the issue". So, fine, whatever, I'll pick it up next week and fill it elsewhere and see if the issue persists.

The truck doesn't throw any sort of code so kinda hard to troubleshoot I guess. Since it doesn't seem to be affecting actual driving I'll give it a few more weeks. I will also listen carefully for the fuel pump on start up, and see if that makes any difference.

00Silverado4x4 · July 26, 2012

Alright, COMPLETELY off chance, is your throttle body loose or any hoses loose or cracked (hopefully not)? I've read some threads about issues running, starting, idleing and some of them point out to vacuum type leaks due to loose/broken hose or parts.

Might be worth looking at, especially since you won't have to pay for it and it's easy to check.

BCMaxima · July 26, 2012

Isn't this the classic symptom of the fuel pressure regulator leaking fuel into the vacuum line... or is this not a problem with the newer trucks?

Big_D · July 27, 2012

im having the same problem. i tried cleaning my MAF sensor the other night. There was a tiny amount of oil on it, prob an over oiled afe filter. anyways i cleaned it(and the filter), seemed to help a little but there's still a noticeable stutter on cold start, maybe 3 seconds then rpms level off. im also burning shell 91 only.

Z45 · July 27, 2012

Fyi - I use Shell gas exclusively in my CTS and my Denali and never have any start issues. Both vehicles start and idle perfectly.

The Shell is located only 1/2 mi from my home while others are 7 or more miles + its pay at the pump.

Svenleven · July 27, 2012

Well, I know it sounds like crap to not be able to gas up at a particular place nowadays, but they did say something to me about alcohol content in my fuel being off somehow. And I tracked it back, and I have been primarily gassing up at Shell (although different stations) for more or less since this issue started (for Air Miles, hahaha). So it's at least worth checking out to be sure.

I won't be picking the truck up until Monday so I'll get more information then. Everything said to me over the phone is a little muddled as I was swinging over from night shift when they called and was pretty tired. I'll see what they have all printed up on the invoice or whatever it's called when it warranty work when I pick it up and try to share the info.

What big_D is describing is identical to my issue, although my truck is completely stock.

If changing brands of gas does fix the issue then there's still a problem as far as I'm concerned, whether its with Shell, or if it's with the GM engine. Maybe this is something particular to the 6.2 where it's hit or miss if you have problems with Shell gas? Or maybe even more specifically Shell gas in Alberta?