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Hesitation On acceleration-code 31,32,51,95

 
Old 06-10-2019, 01:10 PM
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Exclamation Hesitation On acceleration-code 31,32,51,95

So i had my truck sitting for a few weeks (garaged) when I get in to drive it runs great, then, when starting in first gear instead of the RPM's going up they dip down and stall out the engine. I'm thinking Fuel lines ETC. i changed out the spark plugs( cap and rotor, Wires are new) i change out the fuel filter. it got a little better but i still have to High rev to get it to move. once its moving there are no other issues. Now i hear that a vacuum issue could cause sputtering and stalls. however this isn't continuous, just when getting it moving. I checked all the Vacuum lines, elbows, connectors, etc. and found no issues. There were no apparent leaks near or around the Throttle body. I am at a loss.

Details:
1992 F150 flareside 5.0 manual Trans. 2WD
181,000 miles- engine Rebuilt at 105,000 miles
new exhaust set to factory spec with flowmaster muffler
Dual tank - Front(new) rear(original)
I have tried to keep this as close to factory spec since i bought it.
KOEO test codes read 31, 32, 51, 95

any idea where i could start probing to get this thing back to derivable condition?
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Old 06-15-2019, 11:18 AM
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I had experienced something very similar. After lot's of troubleshooting it turned out to be a combination of an O2 sensor and fuel pressure regulator.

My issue started out just like you describe, however, it became progressively worse. It was running lean/rich depending on the driving conditions. It would straighten out after a certain level of high RPM. It would struggle to start well and idle well. I tried just replacing the fuel pressure regulator first since mine was original and that helped a bit, but not completely. I had previously had hooker long tube headers installed and the tech that put the O2 sensor back in the bung didn't do a great job at splicing the wiring. I bought a new sensor and wiring harness to replace it. Runs like a champ now.
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Old 06-15-2019, 02:34 PM
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Originally Posted by Bradlward View Post
I'm thinking Fuel lines ETC.
Are you guessing fuel lines, or did you do some diagnosis that led to a specific problem in the fuel lines? In all these trucks that I've worked on, the only problem I've ever found in a fuel line is collision/fire damage.What is the fuel pressure?


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Originally Posted by Bradlward View Post
i changed out the spark plugs( cap and rotor, Wires are new)...
Before this problem appeared? Or after?
Originally Posted by Bradlward View Post
I checked all the Vacuum lines, elbows, connectors, etc. and found no issues. There were no apparent leaks near or around the Throttle body.
How exactly did you check them? Click this & read the caption:


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Originally Posted by Bradlward View Post
Details...
Put the truck's specifics in your signature so we don't have to dig back through your posts to find them.


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