91 Fox With 4.6 Mark 8 Issues

Discussion in 'SN95 4.6L Mustang Tech' started by Foxy4.6, Jan 30, 2014.


  1. Foxy4.6

    Foxy4.6 New Member

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    Idle air control...i know... put a brand new motorcraft one on today with no luck. along with a throttle position sensor. the motor is 4.6 lincoln mark 8 with an msd dis-4 ignition. K&N cold air. the problem happened randomly about 3 weeks ago while driving home from work and the motor started to sputter out and was near impossible to drive, luckily i was close to home. figured id let it sit overnight.. as i had hoped it started perfectly and went on an hour cruise to make sure all was well, of course having some fun with the right peddle every now and then having no issues until i am almost home again! Now it is at the point where it will barely idle, the motor shakes, and if you touch the throttle at all it dies. 30psi fuel pressure at its attempted idle. all of the wiring to the msd is good, triple checked. throughout the last few days iv replaced the tps, IAC, new msd coil packs and new plugs. the idle slowly got a tad better but not much. also the exhaust smells like fuel. makes me lean towards MAF, but THAT is new too! im stuck scratching my head...any help would be appreciated thank you.
  2. madspeed

    madspeed Colonel Mustard Mod Dude Founding Member

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    Codes, codes, pull your codes


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  3. flstang65

    flstang65 Well-Known Member

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    Fuel pressure should be higher
  4. Foxy4.6

    Foxy4.6 New Member

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    i have not got my hands on a code reader yet, but i turned the fuel pressure up to 35, 40, 45, and 50 with no luck or changes to the problem. the car has ran at 30 psi since iv owned it. it is starting really good but after about 4-5 seconds it dies down to a choppy 500 rpm idle or dies.
  5. Foxy4.6

    Foxy4.6 New Member

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    so heres where i am at...i cant find a diagnostic port anywhere, but i can get the car to idle now. Only if the MAF is UNplugged. I can give it throttle now and it idles around 1200rpm. it runs but not perfect. plug the MAF back in and the idle slows down and eventually gets so low it almost dies and i shut it off. Any ideas..?
  6. madspeed

    madspeed Colonel Mustard Mod Dude Founding Member

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    what computer? Has it ran fine previously?
  7. Foxy4.6

    Foxy4.6 New Member

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    i would think its the computer from the engine donor. says ford on it. iv owned the car for about a year and drive it about once a week with no issues.

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