OX Sensor problems

2001 KIA SPORTAGE
120,000 MILES • 4 CYL • 4WD • AUTOMATIC
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RALPH PHILLIPS
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Sportage 01 (4WD) OX sensors just replaced. looks good for 70 miles then the check engine light comes on and a code of PO 172 ( Too Rich). What would cause that.
Nov 16, 2010 at 10:58 PM
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RASMATAZ
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A code P0172 may mean that one or more of the following has happened:

The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters can cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
There could be a vacuum leak.
There could be a fuel pressure or delivery problem
Possible SolutionsPossible solutions include:

Inspect all vacuum and PCV hoses, replace if necessary
Cleanthe MAF sensor. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
Inspect fuel lines for cracks, leaks, or pinches
Check the fuel pressure at the fuel rail
Check the fuel injectors, they may be dirty. Use fuel injector cleaner or get them professionally cleaned/replaced.
Check for an exhaust leak before the first oxygen sensor (this is unlikely to cause the problem, but it is possible)
Nov 16, 2010 at 11:32 PM
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