1995 ford f150 will not run when hot outside (over 100f)

Discussion in 'The Garage' started by grizzzly, Jun 19, 2017.

  1. grizzzly

    grizzzly The Pre-Banned Version

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    The truck runs good until the outside tempture is over 100f, than it starts sputtering backfiring dying missing and just running like shit. The other day my brother come over to my house as he was driving up I could hear it sputtering and missing. When he got to my place I asked him what was going on? He told me that when it was hot outside (and it was about 104f) the truck just didn’t want to run. We had to do some work on my house and by the time we were done the sun had set and it was about 90f outside. He got into the truck and it started right up and purred like a kitten and he drove off, it ran perfectly. He has had this problem for over a year and it only does it when it is over 100f outside. Last week he drove it to Los Lunas (about 60 miles) and it ran fine but it was only about 95 outside.

    I haven’t had a chance to look at the truck, any ran into this before?
    #1
  2. VX Rider

    VX Rider Long timer

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    Sounds like a form of vapor lock.
    #2
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  3. shovelstrokeed

    shovelstrokeed Long timer

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    Intake air temperature sensor if it is EFI.
    Fuel pump and/or carb float level if not.
    #3
  4. grizzzly

    grizzzly The Pre-Banned Version

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    it is efi
    #4
  5. shovelstrokeed

    shovelstrokeed Long timer

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    OK, check the voltage coming out of the IAT sensor and make sure it stays within specification. There may be other temperature sensors messing with you as well. A hair dryer is a really easy way to simulate hot outside temperatures and see if things go whacky.
    High under hood temperatures can also mess with ignition coils, same tool will find the problem.
    #5
  6. JCool

    JCool Long timer

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    No engine light ?
    #6
  7. PaulTim2000

    PaulTim2000 Been here awhile

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    Ignition coils / HT leads, can be very temperature sensitive when the insulation is starting to fail.
    #7
  8. grizzzly

    grizzzly The Pre-Banned Version

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    i looked at the truck for a minuet but didnt have time to do anything last night. he started it 6 times and it would run good for the first 15 to 20 seconds than start missing and die.
    i hope to have time to screw with it this weekend.
    #8
  9. oldxr

    oldxr Long timer

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    If it has the distributor with the tfi(thick film ignition) module that is usually it.Run it till it quits and check for no spark at the coil wire.If you change that part change the pick in the dizzy too.I used to be a Ford dealer tech-changed a few hundred of these.If you are a Rock auto kind of guy you might just get a reman dizzy.
    #9
  10. scapegoat

    scapegoat Pushin forward back

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    It would be helpful for you to check the fuel pressure at the fuel rail schrader valve when it acts up. I cant recall what year they moved the ignition module off the distributor and mounted it on the drivers side inside fender, but that was a huge big problem with heat failures. Their about $45 but be aware damn near every parts catalog including Ford lists the wrong one for our trucks. If yours is black, get a black one, if its grey, use a grey one otherwise it will run like shit and throw CELs. The pickup inside the dist will eventually go south as well and I dont recall how to check them off the top of my head. Rock auto and numerous other places sell new complete dists for $100 or so but be warned the one I bought once installed left 0 up and down shaft play and may have actually loaded the bottom of the drive gear against the block which eventually will destroy the block and gear due to no oil clearance between the surfaces. I took the ford dist and pirated the new parts from the Chinese RA special and installed them in the OE dist and threw the Rockauto special in the trash.
    #10
  11. grizzzly

    grizzzly The Pre-Banned Version

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    #11
  12. concours

    concours WFO for 44 years

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    Nineteenninetyfive..... carbs had been gone 7 years :deal:freaky
    #12
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  13. severely

    severely almost a noob

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    My money is on the CDI module on distributor, had one do the same thing, grabbed a bag of ice and put directly on CDI module, waited a few minutes. VIOLA. She started and ran to auto parts store for replacement. Might be a good test for your rig. Hope this helps.
    #13