08 Gmc Sierra Rough Idle At Start

[08_GMC_Sierra]

Hey, I'm new to the forums and a new owner of a 2008 GMC Sierra 1500 Extended Cab.

 

I searched but couldn't find anything related to my problem. Has anybody noticed the 4.8 having a rough idle when its started sometimes? I started the truck cold one morning and it had a rough idle and almost sounded like it had a missfire. It cleared up after a few seconds but it hadn't done that before. It had around 600 miles on it when it happend.

 

I changed my oil at 1007 miles and it did it to me again a few miles later. I started it up cold in the morning with my fiance in the passenger seat and she noticed it right away that is wasn't running right. It cleared up after a few seconds and it drives and idles fine for the rest of the day but I don't understand why it's doing it.

 

I haven't seen any check engine lights come on yet. Anybody have this happen to them?

 

Thanks

[MarkPMB]

No help from me, as I only have a couple hundred miles on mine.

I have not noticed anything like that, and I also have the 4.8

[geektoad]

Sounds like it might be CSK. search on CSK, cold start knock, or piston slap.

[fbachman]

First of all, welcome to this forum. I am sure you will find huge amounts of info and input here. Congrats on your new truck.

 

To me, this sounds like a trip to the dealer (unfortuneately). You may have to leave it overnight for them to have a cold soaked engine to try to reproduce it. It is also possible that the pooter threw some codes that the dealer may be able to retrieve and use to diagnose the problem.

 

I have a 5.3. Every now-and-then, I experience a slightly ROUGH idle when cold, but nothing that would get my eyebrows up as what you are describing. It ususally subsides very quickly. I attribute my issue to the choke cycle.

[08_GMC_Sierra]

Thanks for the welcome and the replies.

 

It doesn't sound like piston slap or knocking to me. It just sputters a little and I can see the RPM's fluctuate a little and it goes away pretty quick.

[geektoad]

Thanks for the welcome and the replies.

 

It doesn't sound like piston slap or knocking to me. It just sputters a little and I can see the RPM's fluctuate a little and it goes away pretty quick.

 

That being the case, unfortunately, Frank's probably right. Take it to the dealer and see what they say. Good luck!

[08_GMC_Sierra]

I think it's similar to what Grump Aero Guy's 5.3 does. I have to bring the truck in to get an interior piece ordered that was missing when I got it so I will mention it at the dealer then.

 

I was curious if anybody else experienced this. Thanks for the help.