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Old 07-05-2014, 11:41 AM
wendal wendal is offline
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code P0171

I just bought this 99 f250 super duty with 197k.
I changed all fluids and installed new spark plugs. I then changed the exhaust. I deleted the cat and replaced my muffler with a glass pack. Right after that I got a P0171. The pickup runs rough and jerks when driving it.
I cleaned the MAF sensor. I did replace the fuel filter. I check the pvc hose under the throttle body. It looks good.
What other hoses do I need to look at for vacuum leaks? I have read that it may be my O2 sensor.
It ran pretty good until I changed the exhaust. I did add some marvel mystery oil at the same time.
I did clear the code but still runs rough.
Another problem
My 4x4 light, service engine light does not come on when I turn the key on. All my other light come on then go off. My check engine light never comes on either.
My ABS light is on but I know what the problem is their. The left front wire going to the sensor is broke.

thanks for any help
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Old 07-06-2014, 10:24 AM
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Krewat Krewat is offline
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Something's making it run lean.

Start by checking the fuel pressure, and make sure it's 28-30 at idle, and 38-40 with the vacuum disconnected from the fuel pressure regulator.

Any chance you have an exhaust leak ahead of the O2 sensors?
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Old 07-06-2014, 01:35 PM
wendal wendal is offline
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I will look into the fuel pressure.
I will look at the exhaust but I did not here anything.
thanks again for the help
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Old 07-07-2014, 05:53 AM
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Check the vacuum hoses on both valve covers.
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Old 07-07-2014, 06:40 AM
wendal wendal is offline
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OK will do.
On the passenger side does the hose crack under the insulation? Can I cut it off and then zippy tie it back on?
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Old 07-09-2014, 03:37 PM
wendal wendal is offline
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OK I am sorry for the stupid question but where is the fuel pressure regulator?
thanks
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