What Octane Should I Run Before Heading To Dyno?

Discussion in '1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-' started by 90lxwhite, Oct 12, 2013.


  1. 90lxwhite

    90lxwhite Well-Known Member

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    Does it matter? I usually run 93 but dunno if it helps, hurts, or indifferent.
  2. Mustang5L5

    Mustang5L5 Car used in adult film "Highway Gangbang-InDaButt" SN Certified Technician Founding Member

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    Do you have a tune or any mods requiring higher octane?

    Are you getting a tune?
    stykthyn likes this.
  3. Bullitt347

    Bullitt347 Mustang Master

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    Run the fuel that you normally run, that way the dyno numbers are realistic and if any tuning is done it will be correct for the fuel you always run.
  4. 84Ttop

    84Ttop They make new pistons every day, so why worry? SN Certified Technician

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    Exactly! Use the same fuel you would always use!
  5. 90lxwhite

    90lxwhite Well-Known Member

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    Has been tuned when motor was fresh. But since then had intake and exhaust work but same heads. Reason for going back is to check a/f ratio. Hasn't been runnin to good lately. Smells rich, gassy ya know
  6. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    Have you dumped the codes to make sure there isn't a sensor or wiring problem present?
  7. 90lxwhite

    90lxwhite Well-Known Member

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    Nah she's been on the back burner kinda. Busy w work and ad weather. The o2's aren't that old and neither is maf
  8. f8tlfiveo

    f8tlfiveo My wife likes my spool and blow-off valve.

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    Buy a wideband setup.. They are only 150$-200$ on eBay for a aem or innovate. Then you can monitor it all the time
  9. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    Going to the dyno tune without dumping and fixing the codes is a lot like going out the front door and leaving you pants hanging in the closet. You haven't done everything you need to do to be prepared to go.

    There may be codes that will affect your tune. The turner will charge you $$$ to fix them so that your car can be properly tuned. It is possible that the problems you are having are code related and you can fix them much cheaper than a tuner will do it.


    Dump the codes: Codes may be present even if the Check Engine Light (CEL) isn't on.

    Dumping the computer diagnostic codes on 86-95 Mustangs

    Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.

    Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.

    Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

    Post the codes you get and I will post 86-93 model 5.0 Mustang specific code definitions and fixes. I do not have a complete listing for 94-95 model 5.0 Mustangs at this time.

    Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. On a manual transmission car, be sure to press the clutch to the floor.
    Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.

    [​IMG]

    [​IMG]

    If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

    [​IMG]

    The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

    89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

    [​IMG]

    The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


    WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

    What to expect:
    You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and driveablity problems

    Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

    Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off, and clutch (if present) is pressed to the floor, and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

    Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

    Your 86-88 5.0 won't have a working Check Engine Light, so you'll need a test light.
    See AutoZone Part Number: 25886 , $10
    [​IMG]



    Alternate methods:
    For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

    Or for a nicer scanner see Equus - Digital Ford Code Reader (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30-$36.
  10. 90lxwhite

    90lxwhite Well-Known Member

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    The place that tuned it last time put in an sct chip and they do "free" tunes after the 1st you just pay dyno time. But yeah guess I can dump codes w paper clip to see if there are any.
  11. A5literMan

    A5literMan Advanced Member

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    The Equis-digital code reader link isn't working FYI or it isn't with my iPhone.
  12. 90lxwhite

    90lxwhite Well-Known Member

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    Found one on summit
  13. A5literMan

    A5literMan Advanced Member

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    Cool. Now I can order one. Thanks
  14. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    A5literMan likes this.
  15. madspeed

    madspeed Colonel Mustard Mod Dude Founding Member

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    are you getting a dyno tune or just goingto see what she's got? Many tuners won't touch it if there's fault codes
  16. madspeed

    madspeed Colonel Mustard Mod Dude Founding Member

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  17. 90lxwhite

    90lxwhite Well-Known Member

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    A little of both??? well it had to get tuned after the rebuild awhile back just to get er running due to the cam. At that time it had old rusted out flowmasters due to sitting awhile prior to rebuild. It now has a lil intake and exhaust work so don't really know if it "needs" a time or if they could get anymore out if it w a tune but figurd since a new tune would be free minus dyno time might as well make an appointment and see what happens. But before I go I'm gonna see if it has any codes. Smells rich since the a/c was fixed. "Gassy"
  18. A5literMan

    A5literMan Advanced Member

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