weird start up when cold

[09sierra6.2]

OK!! this is kinda hard to explain unless you hear it for urself in person.. but ima give it a shot anyway!! took out my tune and put truck back to stock i havnt had it on there for bout a week anyway i put some 93 octane at the same place id been getin it from and recently it starts up when the motor has not had any temp in it kinda funny like it has a pause or a hickup.. no poping or backfire but sounds like the backpressure isnt there for a sec then u hear the exhaust and everything is normal and fine.. AM I JUST FREAKN OUT BC I THINK I HEAR SOMETHING.. or is somethin like this i need to take back to the dealer?? it only does this when it hasnt been runinng for a while no matter what time but its only done it here latly when its been bout 45* or colder is it just bc its getin cold its doin it or u think it doesnt have enought backpressure or maybe bc whatever?????

I kno its a lot to read but im freakn out!! theres no codes and when it runs after the start up it wont do it again even if you turn it off imediatly and then do it again its fine and when it warms up its fine! IDK what to do PLEASE HELP!!!

[Poetique]

Sounds like the kinda thing you'll have to record a video of for us to understand, if there's an actual problem.

My truck starts strangely now when it's cold and hasn't been cranked that day, but I already know that's because my ACCrapco battery is terminal and due to die before the year is out.

It's died twice in the last 5 days actually... it can't hold a strong enough charge for more than 36 hours. Probably not even that long if it starts getting into the 30s and 40s again here.

[09sierra6.2]

ya thats what i figured and its weird bc it doesnt sound like its draging on the motor side and if u watch guages they work all fine and how they should but it just has like i said a hesitation just for about 2 secs like it has to get exhasut thru the pipe b4 you can hear it runing.. idk i guess ill try to find a video camera and ill post it up! it kills me to even have the idea of something wrong on my new truck!

[09sierra6.2]

OK so i just realized that i started using 93 octane and thats when this werid start up started, soooooo im thinkn maybe there could b a lil water in it or maybeee idk any suggestions on that???

[Poetique]

Hmm.... not unless the gas came from a different source than you're used to.

Where do you usually get gas, and where did the 93 octane come from?

[09sierra6.2]

two diff places i use to put regular and a bottle of lucas octane booster every now and then with it but i started to put my diablo tune on for 93 octane so i stoped at valaro here in arkansas and filled up and it did it so i held off and thought maybe its just theres so i went to a phillips 66 thats SUPPOSED to be 100% pure gas 93 octane and i put some lucas with it to see if it would clean up and still hasnt so idk.. im thinkn i might run this tank out and try regualr again and see if its the premium gas doin it but if not idk! i usually get gas from the valaro and ive used there 93 before and never had a problem and from shell even tho some ppl dont like shell ive never had any problem with it... However it could be bc its gotten cold here lately but i had an 08 chevy truck and it never did this and neither does my dads 09 tahoe so idk im out of ideas..

[Poetique]

93 octane gas in general is probably fine... the vender may not be. I've never heard of "Valaro..." Sounds like a random, second-tier gas station in which case, that was probably your mistake. Phillips 66 should be fine to my knowledge, but then again, I've never used their brand of gas (Conoco, Phillips, and 76 are all the same... never used any of em).

If you have an Exxon, Amoco, or BP nearby, try their gas. Chevron is good too, just pricey usually. Or if you've got a Mobil nearby, that stuff is epic.

And unless you really just want to use octane booster, it's probably not really doing anything... some of them work a little, sure, but the vast majority don't do anything really.

Although by you saying there's a hesitation on start, it almost sounds like a spark plug issue. But with a new vehicle your plugs basically would have had to have been bad from the get-go. Which is unlikely... but possible.

Edit: Also noticed you have a polished throttle body... if that wasn't done properly, could also be the issue. You havn't tampered with the MAF have you?

Also if you can't tell by now, with this kind of problem, the list of potential causes (if there's even a problem) is epic.

Could be battery (or the terminals... check to make sure they're making good contact and snug), could be the starter, could be spark plugs, could be throttle body related, could be gas, or it could be nothing lol.

In all honesty, if it causes no further problems, and it's only related to the cranking of the vehicle, I'd say don't worry about it too tough...

How cold does it get where you live?

[concoursd]

he meant valero. They are pretty common. Octane booster is known to kill your catalytic converters and oxygen sensors prematurely. I would never use it on my car.

[Poetique]

Ahh, they I have heard of, but not nearly enough for it to register in my brain that that's who he was talking about lol.

Although, if I'm not mistake, they're a discount brand of gasoline are they not? If so... that's still generally a nono, to an extent...

And I agree on the octane booster. Wouldn't touch the stuff. Any marginal amount of power gained even from the ones that do work (like I said, most don't do anything) generally ain't worth it.

[09sierra6.2]

yea sorry for my incorrect spelling i was wore out last night lol... and yea what gets me is it just started it now when its cold and well right now its 28* here in north little rock, arkansas... and the throttle body was done correct and all the terminals are tight and everything is great except that just odd start.. but i was thinkn bout it today and think it could just be the way the motor chokes itself to start seein how it doesnt do it again when it has a lil heat in the motor... and i work at the local oreillys here so its cheap and thought id see if it would help just to try somethin... and i WISH we had a sunoco or exxon, we use to have the exxon but all the exxons here turned in to the VALERO!! and its not the plugs checked those and the wires arent it those are MSD wires ive had on there and they run fine! put the stocks back on and same thing so im really thinking its maybe a choke sound im hearing..

[SparkySparks]

Valero buys gas from other companies, they don't have there own refineries or maybe its oil in general. I work for an engineering company that does lots of work for oil companies and Valero put projects on hold a wile back and the reason I was told was cause they buy oil/gas from other companies. I only used them once or twice and my mpg went down so I stay away from them now. I try to stick with Marathon or BP.

[09sierra6.2]

ya i guess ill stick with phiilips 66 its the best gas i can find in my area anyway without drivin for a good ways... thanks for tunin in and tryin to help me but i think im just bugin.. if it dont get better ill take it back to the dealer!