×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Why does a car sputter when cold?

Why does a car sputter when cold?

Why does a car sputter when cold?

(OP)
I have read about temp sensors, fuel mixes etc but I am wondering why does it actually happen, surely once the pistons and valves etc have turned over and have run for a few seconds they should run smooth, what is it about cold weather that makes the engine run differently? Is it a question of contracting metal? A 20 degree Celsius change in engine temp surely cant affect the fiction of the metal parts?

RE: Why does a car sputter when cold?

It's almost completely due to poor air/fuel mixture formation. Cold fuel has a low vapor pressure and a lot of it remains liquid and does not mix with the air or burn. There is a huge cold start enrichment to make up for it whether it's a mechanical choke in carburetors or simply programed in delivery adjustments in EFI. Many of the advances in cold start emissions reductions have to do with improved mixture formation, the others have to do with faster warm up. There are some additional friction losses due to pumping cold oil but that is just a relatively small parasitic loss.

Most modern fuel injected cars run very smoothly right from the start although they will have an elevated idle speed and they are running richer than normal.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Why does a car sputter when cold?

(OP)
Thank you dgallup, that does help me.

Garth

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

White Paper – Data Security and Know-How Protection
Our data is constantly exposed to the danger of being intercepted or stolen as it wends its way over global data networks. Data security measures and measures for protecting intellectual property should not, however, first be implemented when data is exchanged – companies must lay the foundation for these measures within their own organization. Download Now
White Paper – Collaboration in the PLM Context
The influence exerted by the Internet of Things (IoT) means that there is a steadily growing need for collaboration in industry. Partners from new industries and areas of application need to be integrated in cross-company business processes to ensure that the lifecycle of smart, connected products can be managed from end to end. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close