Running rough when cold

2004 GMC YUKON
160,000 MILES • 5.3L • V8 • 4WD • AUTOMATIC
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CHEVROLET 1988
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  • 1 POST
The vehicle listed above is an xl model. It runs rough when cold like it has a bad misfire smooths out when warmed up and engine pulls down bad when waiting at a redlight like it's about to shut off.
Apr 1, 2022 at 5:18 PM
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JACOBANDNICKOLAS
  • AUTOMOTIVE REPAIR CONTRIBUTOR
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Hi,

Does the low idle happen only when it's cold? Also, have you checked for engine vacuum leaks? If not, start with that first. Take a look through this link. It explains how to locate and repair an engine vacuum leak.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Next, by chance do you have a live data scan tool? If you do, let me know what the short-term fuel trims are when it runs rough. Also, before starting the engine for the day, see if the engine coolant temperature sensor signal indicates a temperature very close to the ambient temperature.

Let me know what you find or if you have other questions.

Take care,

Joe
Apr 1, 2022 at 10:24 PM
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