Notices
2007 - 2013 (GMT900) Section for all discussion related to the 2007-2013 Chevrolet and GMC trucks.

Cold start issue

Old January 13th, 2019, 10:52 PM
  #1  
CF Beginner
Thread Starter
 
Join Date: Jan 2019
Posts: 2
Default Cold start issue

2008 Chevrolet Silverado 1500 5.3 liter vortec 4x4.
Rough idle (Signifigant bouncing rpm) for 15-45 seconds when cold started. Once warm it runs and idles perfect.
Not throwing any codes.
Was just at the mechanic for new AFM and normal valve lifters.
It has new machined heads and *new* intake and exhaust gaskets. New spark plugs.
Problem started 3 days after the $4000 repair.

The thottle body has been cleaned, idle relearned, codes reset my shorting battery terminals, sensors checked and mechanic has tried swapping "multiple components" and doesn't know what to do.
Wants to send it to a dealership for computer reflash and go from there.

Mechanic did do a unlit propane test at intake gasket, but I'm not sure if it was during cold start or after it had warmed up. I have video of how it sounds if there is a way to send it to you. Didnít work to attach.

Looking for anything to help us troubleshoot this. Huge thanks in advance.
Colette Hayes is offline  
Old January 13th, 2019, 11:29 PM
  #2  
CF Veteran
 
oilcanhenry's Avatar
 
Join Date: Oct 2017
Location: USA
Posts: 1,431
Default

Originally Posted by Colette Hayes View Post
2008 Chevrolet Silverado 1500 5.3 liter vortec 4x4.
Rough idle (Signifigant bouncing rpm) for 15-45 seconds when cold started. Once warm it runs and idles perfect.
Not throwing any codes.
Was just at the mechanic for new AFM and normal valve lifters.
It has new machined heads and *new* intake and exhaust gaskets. New spark plugs.
Problem started 3 days after the $4000 repair.

The thottle body has been cleaned, idle relearned, codes reset my shorting battery terminals, sensors checked and mechanic has tried swapping "multiple components" and doesn't know what to do.
Wants to send it to a dealership for computer reflash and go from there.

Mechanic did do a unlit propane test at intake gasket, but I'm not sure if it was during cold start or after it had warmed up. I have video of how it sounds if there is a way to send it to you. Didn’t work to attach.

Looking for anything to help us troubleshoot this. Huge thanks in advance.
Sounds like might be a small intake leak that seals when engine is warm to me. Might be a good idea to re- torque your intake manifold and check everything for tightness.
oilcanhenry is offline  
Old January 14th, 2019, 8:48 AM
  #3  
CF Beginner
Thread Starter
 
Join Date: Jan 2019
Posts: 2
Default

Thank you so much! Will definitely check into that potential issue. Much appreciated man!
Colette Hayes is offline  
Old January 15th, 2019, 9:10 AM
  #4  
CF Veteran
 
oilcanhenry's Avatar
 
Join Date: Oct 2017
Location: USA
Posts: 1,431
Default

Originally Posted by Colette Hayes View Post
Thank you so much! Will definitely check into that potential issue. Much appreciated man!
You are quite welcome..
oilcanhenry is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: