2010 Gmc Sierra Cold Start Problem

[RandyD123]

I was haveing problems when cold starting my 2010 GMC Sierra SB/RC. It would misfire on all cylinders during a cold start then within seconds run fine. If I shut it off right away and started again it would be fine. There were no trouble codes and a regular On-Star diagnostic said the truck was fine.

 

I brought it to the local dealer and they confirmed the problem but even with thier OBD computer they showed no trouble codes. The problem turned out to be a Flex-Fuel sensor. It showed the I was running 58% alcohol mix when in fact a dealer fuel test showed the mix was really just 8% alcohol. They reprogrammed the computer and sensor.....now it's been perfect.

 

Just a heads up if you experience this problem

[maxco]

I was haveing problems when cold starting my 2010 GMC Sierra SB/RC. It would misfire on all cylinders during a cold start then within seconds run fine. If I shut it off right away and started again it would be fine. There were no trouble codes and a regular On-Star diagnostic said the truck was fine.

 

I brought it to the local dealer and they confirmed the problem but even with thier OBD computer they showed no trouble codes. The problem turned out to be a Flex-Fuel sensor. It showed the I was running 58% alcohol mix when in fact a dealer fuel test showed the mix was really just 8% alcohol. They reprogrammed the computer and sensor.....now it's been perfect.

 

Just a heads up if you experience this problem

 

Wow thanks man. The last couple weeks my truck ('10 Sierra) has been doing the same thing... I will have to check that out.

Thanks for the heads up.

[crankman]

Thank you Randy outstanding tip hope i dont need it but good info.

[fraiolib]

ahhhh mines been doing the same thing, and ive actually had a problem with that, justin at black bear noticed it in one of my data logs.... i just never put the two together, rite after it fires (cold) it almost dies than picks rite back up and runs fine.

[jarettg]

i had the same problem, just got back from the dealership. they stated that the fuel trim was out of wack. they said after filling the tank i should drive for at least 20 min before parking it. they stated that the engine doesnt have time to calculate how much alcohol there is in the fuel.

 

thing is that i have been getting the same gas from the same company for the past 6-8 months...weird. anyways its working fine now.

 

i have read on some other forums that this can also cause some smoke to come from the exhaust on start up. i have noticed a slightly blue/gray smoke on startup the other day, we will see if it ceases now that the problem is fixed.

[SouthCo]

I've been lucky and haven't had any of the symptoms noted in the this thread but thanks for posting. I know some shops have trouble diagnoising problems with a code. At least if it ever happens to mine I can give them a suggestion. Again, thanks.

[RandyD123]

So my problem is back except this time it seems to be more tempature specific. When it's around 30 degrees or so it seems to start fine but between 30 and 50 it misfires and then starts. I guess back to the dealership. I will report back when I bring it in this week!!!

[tazerbro]

Any update on this? My truck is beginning to do the same....Blackbear tuned and Running E-85...

[SouthCo]

Mine started doing this a few weeks ago too. I don't know if its because it started getting colder or if its just a coincidence. I haven't taken it in to the dealer because of the bb tune. I guess I'll have to put the stock tune on soon and take it in.

 

 

Sent using Tapatalk

[tazerbro]

We all have the same trims and I'm thinking this isn't a coincidence. It does NOT feel normal. My engine should definitely not be doing this...

[BlackZ71Silverado]

What kind of fuel are you guys running that are having this problem??

 

Brand? Grade?

[tazerbro]

What kind of fuel are you guys running that are having this problem??

 

Brand? Grade?

 

 

I run E85 currently. Buy it from Meijer

[tazerbro]

I'm getting ready to start it after sitting all night and with it being 30 degrees outside and do a datalog with the Autocal. I'll send it over to Blackbear and see if they've got any ideas before taking it to the dealer. It only does it first start up. I'm thinking it has something to do with the cold weather and maybe the E85....I made the mistake of putting it in drive the other day when it was acting up and the extra strain just made it die. My truck is overdue for an oil change, too

[GMCustomerService]

CoreySP,

 

Keep me posted on your progress. Let me know if you need anything.

 

Tricia, GM Customer Service.

[tazerbro]

While in the auto parts store today, I purchased a bottle of this stuff and added it to an entire tank of E85. Will update to see if I noticed a difference. I've run E85 80% of it's 21k miles.

 

 

http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_x_10057630-P_x_x