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.
Friday, October 1st, 2010 AT 8:35 AM

7 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Have you checked fuel pump pressure? Also, any vacuum leaks?
Was this
answer
helpful?
Yes
No
Friday, October 1st, 2010 AT 11:31 AM
Tiny
KIMPAK
  • MEMBER
  • 3 POSTS
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?
Was this
answer
helpful?
Yes
No
Friday, October 1st, 2010 AT 11:51 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Yes, but they usually will turn the check engine light on. Has it come on?
Was this
answer
helpful?
Yes
No
Friday, October 1st, 2010 AT 1:14 PM
Tiny
KIMPAK
  • MEMBER
  • 3 POSTS
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.
Was this
answer
helpful?
Yes
No
Friday, October 1st, 2010 AT 1:21 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
The lean mixture could come from a vacuum leak, O2 sensor. If you get a chance, let me know what the codes were.

Joe
Was this
answer
helpful?
Yes
No
Friday, October 1st, 2010 AT 11:32 PM
Tiny
KIMPAK
  • MEMBER
  • 3 POSTS
Here are the exact codes the computer returned.
P0171, p0174, p1132, p1152
Was this
answer
helpful?
Yes
No
Saturday, October 2nd, 2010 AT 11:18 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
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?
Was this
answer
helpful?
Yes
No
Sunday, October 3rd, 2010 AT 3:22 PM

Please login or register to post a reply.

Related Engine Hesitate Content

Vacuum Leak Test and Repair
VIDEO
Vacuum Leak Test and Repair
Instructional repair video
Hesitation
GUIDE
Hesitation
An engine hesitation is an interruption of continuous power during acceleration. When a engine is hesitating it will cause the car to lunge or surge which will cause a...
VIEW MORE