Running Rich, Jerking At Low Rpms And Surging Idle

Discussion in 'Fox 5.0 Mustang Tech' started by nogoodgt, Jul 20, 2014.


  1. nogoodgt

    nogoodgt Member

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    Hello i have a 89 GT h/c/i #30 injectors 70mm tb. A/C EGR Power steering smog and heat stuff is all deleted. new stuff TPS and IAC. theres no check engine light in the dash and all after market phantom 2 gauges. bought the car 2 years ago blown up so this is after the rebuild nothing changed just built alot better then it was. now with maybe 12 miles on and the plugs are black. it runs alot better with the maf unplugged. the cap on the maf says pro-m 75mm and 30#. but the top cap has been tampered with so i tested a stock 5.0 maf and it ran the same. please Help

    if you need more info just let me know. Thanks
     
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  2. jka

    jka Member

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    What cam are you running? It could be the timing because you can advance the timing too far and the car will buck and jerk. Did you try to retard the timing? And do you have an adjustable fuel pressure regulator?
     
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  3. nogoodgt

    nogoodgt Member

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    F303 timing is dead on used to have a bbk fpr now has stock.
    bbk one got blown out. And the idle goes from 1300 or so to 400 up and down and stalls
    And if try to back it out of the drive way it just dies

    also a manual car
     
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  4. Noobz347

    Noobz347 Stangnet Facilities Maint Tech... Er... Janitor Admin Dude

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    You're going to have to pull codes man. There's a LOT going on there and codes can help narrow down a starting place.

    You're at what I consider to be the limit of running a calibrated MAF due to the size of your injectors. Sometimes 30s will work while other times it won't. There's more to tuning for large injectors than what can accounted for with just a MAF.

    30s can be hit or miss but that doesn't mean that this is YOUR specific problem.


    Also look at @jrichker 's post at setting idle. It may help. Try opening the throttle body a bit more at idle.
     
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    Last edited: Jul 20, 2014
  5. nogoodgt

    nogoodgt Member

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    btw if i pull the tune out it still run the same its like its in a limp mode all the time a just dumping fuel. And i cant drive the car to get the computer to read codes. but still idles alot better without the maf.
     
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  6. Noobz347

    Noobz347 Stangnet Facilities Maint Tech... Er... Janitor Admin Dude

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    It goes to safe mode when the MAF is disconnected. You don't need to drive to get codes. Just idle.
     
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  7. nogoodgt

    nogoodgt Member

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    it doesn't idle for crap and drink so much fuel even at idle its stupid. i also don't want to hurt the nice hone and rings. but yes i have been trying to and it wont give me codes :(
     
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  8. Dave2000GT

    Dave2000GT Active Member

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    Sounds like that car got the living **** beaten out of it.
     
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  9. stykthyn

    stykthyn Commander of the snuggie cultists

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    Your first and biggest problem is why you can't pull codes. No sense chasing anything else yet.
     
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  10. madspeed

    madspeed Colonel Mustard Mod Dude Founding Member

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    Pull codes and go from there
     
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  11. nogoodgt

    nogoodgt Member

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    im about to try and pull codes it might be the scanner as well.
     
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  12. nogoodgt

    nogoodgt Member

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    still cant get it to pull codes. i pulled the o2s and it ran the same
    also runs the same with tune out of the computer and 02s in
     
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  13. Noobz347

    Noobz347 Stangnet Facilities Maint Tech... Er... Janitor Admin Dude

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    Take a stab what your first priority is.
     
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  14. nogoodgt

    nogoodgt Member

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  15. Noobz347

    Noobz347 Stangnet Facilities Maint Tech... Er... Janitor Admin Dude

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    You have to start looking into why you can't pull codes.

    An EEC that is incapable of returning trouble codes may VERY WELL be an EEC that is malfunctioning.

    There are NO OTHER troubleshooting procedures to do until you can verify that the EEC is functioning properly. If no codes are present then you should get a code-11 indicating that the EEC is functioning.

    Without that code-11, it is useless to look at any other component.

    See the following link:
    http://www.stangnet.com/mustang-forums/threads/help-me-create-the-surging-idle-checklist.698148/
     
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  16. nogoodgt

    nogoodgt Member

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    i found that my maf ground is connected to the num 1 pinout kapwr somewere can this cause this looking into the wiring right now.
     
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  17. Gearbanger 101

    Gearbanger 101 Straight Outta Locash Super Mod

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    You should at the very least be able to do a KOEO test. Ya don't need the car running for that.
     
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  18. nogoodgt

    nogoodgt Member

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    should the black and green maf ground have continuity with 40 pin and number 1 pin keep alive memory.
     
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  19. nogoodgt

    nogoodgt Member

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    man this car is killing me
     
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  20. stykthyn

    stykthyn Commander of the snuggie cultists

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    You will figure it out. And in the end you Will be glad you did.
     
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