running rich

2003 JEEP GRAND CHEROKEE
113 MILES • 6 CYL • 4WD • AUTOMATIC
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GEOFFHAHA
  • MEMBER
  • 1 POST
i just changed the spark plugs on my 03 grand cherokee 4.0l last week and the front three plugs are covered in carbon deposits where as my back three are not...what could cause that
Jul 27, 2011 at 2:23 PM
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CJ MEDEVAC
  • ✓Experienced Mechanic
  • 11,000 POSTS
FOUND THIS FOR YOU

http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp

DOES THIS HELP?

THE MEDIC
Jul 29, 2011 at 1:46 PM
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RASMATAZ
  • ✓Experienced Mechanic
  • 75,988 POSTS
Probable causes of an engine running rich are as follows:

1.Excessive fuel pressure can be cause by restricted fuel return line
2.Defective Oxygen Sensors.
3.Leaking injectors and fuel pressure regulator.
4.Coolant temperature sensor out of calibration.
5.Restricted air intake system.
Jul 29, 2011 at 1:48 PM
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