technical help please 95 5.0 at the end of my rope lol

Discussion in '94-95 5.0 - Specific' started by nubbyless, Oct 26, 2018.

  1. nubbyless

    nubbyless New Member

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    Hi i have a 95 mustang vert 5.0 H.O. 5spd idle is erratic sometimes it idles 650 to 700rpm perfectly smooth then randomly starts surging up and down then sometimes it will race up to 2000rpm without touching anything stay there
    for 30 seconds or so then fall back down and start surging again then smooths out.

    While driving sometimes while driveing at a smooth even speed suddenly it feels like another cylinder or two came on sudden surge of more power then
    drops back to normal.

    things i have done checked for vacume leaks cant find any unless under the intake havent removed that yet

    parts changed all original brand new parts
    pcv valve and filter
    air temp sensor
    coolant temp sensor
    iac valve yes mtorcraft
    tps
    egr and egr sensor
    cap rotor plugs wires and coil (tried multiple caps rotor wires)
    fuel pressure regulator
    fuel filter at tank
    driver side 02 sensor

    things not changed
    fuel pump (pressure seems fine)
    ignition module had it tested at pep boys on their computer tested good 12 times in a row
    distributor is there any way i can check it
    passenger side 02 sensors
    maf i did clean it though
    is there something else im missing in this list

    i did the proper idle setup procedure including letting it idle for 10 to 15 minutes to learn its idle
    i hate just throwing parts at it like that but i dont care at this point i just want it to run correctly.

    Any ideas
     
    Last edited: Oct 26, 2018
  2. ttocs

    ttocs Legend

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    You say the fuel pressure is fine, what is it at? Have you smoke tested it to look for vac leaks?
     
  3. evilcw311

    evilcw311 Well-Known Member

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    Yes please explain how you vacuum tested?!? How did you clean the maf?!? Have you checked it for any codes??


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  4. nubbyless

    nubbyless New Member

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    I have nothing to smoke test just tried spraying carb cleaner and water everywhere waiting for idle change I also changed many of the vacuum lines ones I could get to clean maf with maf spray twice no codes on reader and no engine light
     
  5. ttocs

    ttocs Legend

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    smoke test is easy to do there are a bunch of videos on youtube that show how to do it with a cigarette and a bottle. Also how did you check fuel pressure?
     
  6. evilcw311

    evilcw311 Well-Known Member

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    Where are you located?


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  7. ttocs

    ttocs Legend

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    also curious, were you using the obd2 port on the console to pull codes like everyone tries to the first time?
     
  8. 96blak54

    96blak54 Legend

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    You guys are harsh!
     
  9. ttocs

    ttocs Legend

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    hey I asked cause I did it the first time I tried to check codes. It was 1994 when I did it but I did it and was all confused.
     
  10. nubbyless

    nubbyless New Member

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    Tested with odb1 test port on passenger shock tower port works it goes through the tests fine fans kick up etc. For fuel pressure I used a fuel pressure test gauge connected on the Schrader valve if I remember correctly it was 43lbs at idle with vacuum line off. I will look into the smoke test with the bottle and cigarette I live in Florida near Tampa area
     
  11. evilcw311

    evilcw311 Well-Known Member

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    Well crap, kinda far to drive and help. Lol

    Start with smoke test and let us know how that goes.


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  12. ttocs

    ttocs Legend

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    sounds good so far. Try the smoke test and see if that shows any leaks.
     
  13. Wood's 5.0

    Wood's 5.0 New Member

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    What modifications have been done to the car?
     
  14. dcm0123

    dcm0123 New Member

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    The sudden increase to 2000 rpm may be caused because the computer sensing something is out of bounds so it increases the speed to compensate for it.
    You may want to try turning in the throttle plate screw which sets the minimum opening about 1 turn and see if it helps. Turn it in, turn off the car and restart so everything resets itself.
    I had problem with surging idle and it was because the plate was open to far so when the computer tried to increase the idle, it overshot the desired speed, then it would drop back down, then repeat.