Rough Idle

2002 GMC SIERRA
170,000 MILES • V8 • 4WD • AUTOMATIC
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MICHAEL MCWHERTER
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  • 1 POST
I have a 2002 GMC Sierra, with a 5.3 V-8. In cold temperature, when I first start my truck, it immediately idles up to 2300 rpm for about 3 seconds, then drops to about 700 and idles really rough until it warms up. It does set trouble codes--lean mixture both banks, and multti-cylinder random misfire. I'm concerned about it idling so fast before it picks up oil pressure. Any ideas?
Dec 8, 2010 at 7:04 AM
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HMAC300
  • ✓Experienced Mechanic
  • 48,601 POSTS
check the fuel pressure and have the compression checked on misfire cylinder along with normal ignition checks. don't worry about any damage to engine. there is residual oil on the bearings and no damage will occur. the manufacturer has tested for things like that more than you can ever imagine.
Dec 8, 2010 at 7:29 AM
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JACOBANDNICKOLAS
  • ✓Experienced Mechanic
  • 110,248 POSTS
If you have a lean mixture, check for vacuum leaks. Let me know if you find any.
Dec 8, 2010 at 7:29 AM
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