87 Mustang Lx Hesitation

Discussion in 'Fox 5.0 Mustang Tech' started by nicdec19, Dec 24, 2013.

  1. nicdec19

    nicdec19 New Member

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    alright, im new here but not to cars and im having trouble with my 87lx 5.0 symptoms are hesitation,popping,missing,backfiring under load when warm. sometimes when i mat the pedal it will start missing then it will take off like a rocket. i just replaced plugs,wires,cap,and rotor as well as the fuel filter and ect sensor
     
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  2. stykthyn

    stykthyn Commander of the snuggie cultists

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    Pull codes
     
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  3. jrichker

    jrichker StangNet's favorite TOOL
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    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 www.midwayautosupply.com/Equus-Digital-Ford-Code-Reader/dp/B000EW0KHW Equus - Digital Ford Code Reader (3145It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $22-$36.
     
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  4. madspeed

    madspeed Colonel Mustard
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    moved to tech
     
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  5. nicdec19

    nicdec19 New Member

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    i checked for codes and it didnt have any, i did find a missing hose to the map sensor from the intake manifold, not sure if that fixed the problem havent been able to drive it much because of the weather
     
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  6. Mustang5L5

    Mustang5L5 Car used in adult film "Highway Gangbang-InDaButt"
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    That probably should have generated a code.

    Your car wasn't converted to Mass Air was it?
     
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  7. jrichker

    jrichker StangNet's favorite TOOL
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    No code 11 (two flashes when the computer dumps the codes)? A perfectly functioning system will always get a code 11, it is the everything is OK code. The 11 code is computer passed its internal self test.
    If you don't get an 11, you have computer or wiring problems.
    Please check and repost.
     
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  8. nicdec19

    nicdec19 New Member

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    i had a buddy of mine take it to his work and use a scan tool and he said he didnt get any codes at all, and no its still speed density
     
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  9. nicdec19

    nicdec19 New Member

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    Nevermind what I just said I just talked to him and he said he got that and the scan tool said test passed
     
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  10. madspeed

    madspeed Colonel Mustard
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    koer codes? cylinder balance test?
     
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  11. nicdec19

    nicdec19 New Member

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    The missing hose from the map sensor seems to have helped it hasn't backfired at all since then and the hesitation is a lot better
     
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  12. nicdec19

    nicdec19 New Member

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    I also have replaced the ignition coil and ignition coil connector pigtail
     
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  13. jrichker

    jrichker StangNet's favorite TOOL
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    No code 11 (two flashes when the computer dumps the codes)? A perfectly functioning system will always get a code 11, it is the everything is OK code. The 11 code is computer passed its internal self test.
    If you don't get an 11, you have computer or wiring problems.
    Please check and repost.
     
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  14. nicdec19

    nicdec19 New Member

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    Yes he got that and the scan tool said test passed
     
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  15. 7991LXnSHO

    7991LXnSHO Well-Known Member

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    Checking all the vac lines and for other other vac leaks would have been my next step on carb or efi. Leaving the big cap off of the underside of the upper intake intake caused all kind of crazy issues. All those rubber and plastic lines and rubber caps could be cooked crispy by now.
     
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  16. nicdec19

    nicdec19 New Member

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    im thinking something isnt advancing the timing, thats what it feels like im thinking either distributor/tfi (the rotor seems to have excessive play) or maybe a bad sensor either tps or map. pretty sure its not a fuel issue because it was backfiring through the exhaust and checked the pump pressure running and it was 40psi but key on engine off it was only 25psi, starts fine though.
     
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  17. Mustang5L5

    Mustang5L5 Car used in adult film "Highway Gangbang-InDaButt"
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    He ran the test twice right?

    One with engine off, and one with engine running?

    I Only ask because getting three code 11s on a fox body is pretty rare. There's always a minor code or two stored. That's why you see so many posts questioning how the test was performed.
     
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  18. Mustang5L5

    Mustang5L5 Car used in adult film "Highway Gangbang-InDaButt"
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    Also, could you please list the modifications from stock that the car has done to it? (Engine wise)
     
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  19. Casey Young

    Casey Young Member

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  20. nicdec19

    nicdec19 New Member

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    new coil
    Not sure I'll have to ask
     
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