Rough idle in cold weather

Is there any modifications to the intake, engine or exhaust. If not I would check which ever sensors were not fixed. If you have lots of mods than you may need some things changed in the PCM, but it sounds like an issue under the hood to me. Something small like this will be hard to find becasue it doesn't sound like a hardware failure just a bad reading during the engines warm up. The fastest way to find and repair it will be with a scan tool that can read live data from your motor. Otherwise it's just random guessing. Record the values of each sensor/output when the truck is idling rough then start it again later when it's cooled off enough to run right but not cold enough to have the issue. Do you have a list of the sensors you replaced??

I will look and see if I still have all the receipts. It started this 4 years ago and every winter they try something else, but it never made the Service Engine Soon light come on until this week so they were never able to get a code. The codes this week were PO171 and PO507. He said he checked all the sensors and they are checking good. I know sometimes in the mornings after if has done its reving up and down I can smell fuel like it is flooded. I would think if it was a computer update needed it would do it all the time.

To answer you on the modifications. I had dual exhaust put on it in 2006 nothing else has been changed on it

Sorry, the exhaust was put on in 2004 and it has 118,000 miles on it so it isn't really high milage.

Codes only tell you when there has been a failure or something is way out with the way your engine is running. Live data is where you can pin point sensor computer issues. It would also tell you if you need a re-flash. Quick run down on the efi system. Your engine uses the input from the sensors to control the outputs. For the fuel injectors the PCM matches the input values (sensors) to the applicable table(s) and delivers the required fuel for the current engine condition, called open loop. For the most part these are set at the factory or changed with a programmer or by a tuner. Once the engine warms up it switches to closed loop were the oxygen sensors can add a trim to your fuel calculation to adjust the air/fuel ratio and make it run better. For the most part the tables are fine with the stock values and it is usually a failure somewhere that causes the issues, but if you make drastic changes to the engine and it's components then you need to modify. I doubt the dual exhaust is causin the issue and it is most likely a failure causing you to run rich until you warm up and hit "Closed loop" I'd check the engine coolant sensor first?

Thank You I will have it checked

Hi all, I also experience this same issue with my 2001 GMC 1500 and I am going to try fuel injector cleaner. I could be way off and wasting my $2.99 but my theory is the "gunk" build up on the injectors. I'm thinking the particles in the build up are freezing and creating crazy spray patterns to the heads. I could be crazy but its worth a try!

If you live in a cold winter area you may need to switch to a winter weight oil. I agree with the above poster - try some fuel system cleaner - you have nothing to lose.

It turned out to be bad manifold intake gaskets. Had it fixed last January and has been running fine since then

I’m also experiencing the same issue with my 2000 Chevy Silverado 1500. I moved from Florida to upper California and it started doing it on the winter . Never does it in the summer but always does it on the winter . So hopefully I can find the solution.

Vacuum leak

The vacuum leak sounds different than what my pick up sounds like when i started up in cold conditions

Intake gasket leak same as vacuum leak needs intake gaskets

Ok thanks cuz there’s oil around head gaskets so your right