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1996 Ford F-150 Random engine hesitation

Tiny
KIMPAK
  • MEMBER
  • 1996 FORD F-150
  • V8
  • 4WD
  • AUTOMATIC
  • 86,000 MILES
I have a '96 F150, randomly during long trips in particular the engine will start hesitating and lose power and can't get above about 40mph. Stopping, turning the key off and then restarting will fix the problem and it runs perfectly normal. Last time this happened it lit the check engine light. The Code indicated a bad fuel/air mix being too lean. When I cleared the code and went for a test drive the light stayed off.
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Friday, October 1st, 2010 AT 8:35 AM

7 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Have you checked fuel pump pressure? Also, any vacuum leaks?
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Friday, October 1st, 2010 AT 11:31 AM
Tiny
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I haven't, but I'm thinking it could be more of a sensor issue, considering it magicly fixes itself when I turn the key off and back on. However, I'm not a very experienced mechanic, so I could be way off. Is there a sensor, that, if bad could cause this symptom? Something that controls the fuel/air mix maybe?
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Friday, October 1st, 2010 AT 11:51 AM
Tiny
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Yes, but they usually will turn the check engine light on. Has it come on?
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Friday, October 1st, 2010 AT 1:14 PM
Tiny
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Yes the light did come on the last time it happened. I checked it with a computer and the two codes it turned up was "fuel lean" and something about air mixture. I'm not at my home desk to check what the exact code is at the moment.
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Friday, October 1st, 2010 AT 1:21 PM
Tiny
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The lean mixture could come from a vacuum leak, O2 sensor. If you get a chance, let me know what the codes were.

Joe
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Friday, October 1st, 2010 AT 11:32 PM
Tiny
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Here are the exact codes the computer returned.
P0171, p0174, p1132, p1152
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Saturday, October 2nd, 2010 AT 11:18 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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P0171
Fuel Trim System Lean (Bank 1)

P0174
Fuel Trim too Lean (Bank 2)

P1132
Lack Of HO2S Switch - Sensor Indicates Rich

P1152
Lack Of HO2S21 Switch - Sensor Indicates Rich

This is odd. It seems like the O2 sensors are over compensating for a lean mixture. To me, I would be looking for a major vacuum leak. Have you checked for that?
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Sunday, October 3rd, 2010 AT 3:22 PM

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