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  1. #1



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    Car sat, now runs rough. What do I check?

    98 GT ran great when I put it on jackstands a year and a half ago for a two month project. Finally got it on the ground. Fuel pump didn't work, so replaced that. Fuel filter has less than 2,000 miles on it, was clear when I put it back last month. The car will fire up, but won't idle. The rpm would peak up to 3k then drop down, stumble, and die once started even with no throttle. Touch the throttle, revs super fast but won't steady at any one speed. I checked for vacuum leaks. Replaced the IAC, almost no improvement.

    Touched positive and negative battery cables together for 30 seconds to reset the computer on advice of my local mechanic. It is better, will idle rough for 30 seconds before dying, still revs too high if I touch the throttle. Stock except for Accufab plenum and 70mm throttle body that was rebuilt and calibrated at the factory before install, BBK CAI, Ford Racing wires, Screamin Demon coils. Ran great when I parked it. I'm out of ideas. Any suggestions?


    "I'm not a complete idiot - some pieces are still missing "

    98 GT ragtop 5-speed in Chrome Yellow - mine
    98 GT ragtop auto in Pink - wife's

  2. #2



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    Did you check the TPS voltage after you installed the throttle body? What did they calibrate at the factory?

  3. #3


    ttocs's Avatar
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    replace the gas or was that a year old as well?
    https://driiive.com/ttocs/1994FordMu...!/gallery/add/
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  4. #4



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    Gas was not fresh, but it was treated with Sta-bil. I had to drain the almost-full tank for the fuel pump swap and dumped several gallons in my daily driver and fueled up my mowers with no problems. I had sent the throttle body to Accufab to check adjustment, they said the shaft was worn so rebuilt the whole thing for just the cost of shipping (shout out to Accufab customer service!) including adjusting the trottle blade opening screw. It ran great after I put it back in. I just tried loosening the TPS and rotating it a little, no luck. Not sure how to check voltage...
    "I'm not a complete idiot - some pieces are still missing "

    98 GT ragtop 5-speed in Chrome Yellow - mine
    98 GT ragtop auto in Pink - wife's

  5. #5



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    I know the pump is new, but check the working pressure anyway. Does plugging/unplugging the maf make a difference?

  6. #6


    96blak54's Avatar
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    Sounds like a tps fail. Try unpluging things one at a time to see if there is an improvement.

  7. #7


    ttocs's Avatar
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    tps is easy to check voltage. Set the meter to DC voltage and if I am not mistaken you check the 2 wires on the outside(I think there are 3?). With the key on, slowly move the TPS and make sure the voltage change is gradual and there are no spots were you read an open circuit/no voltage.
    https://driiive.com/ttocs/1994FordMu...!/gallery/add/
    Sponsored by: Redline Leather Goods http://www.redlinegoods.com/
    ____________ Mishimoto Automotive http://www.mishimoto.com/

  8. #8



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    I forgot to add the brake pedal went to the floor. I had set with my local mechanic, who knows the car, to look at it today. I was able to get it started and had some brakes at full pedal, so limped it to the garage under its own power. I forgot how good this car sounds! Anyway, other than the brakes, rough running, and what feels to be a minor drivetrain vibration, it drove good. I had put lowering springs, Cobra brakes, Konis, and sway bar bushings up front up front with Kenny Brown plates, and in the rear aftermarket ucas and lcas, lowering springs, complete Cobra rear with 3.73s and Cobra brakes to replace my GT 3.08 axle and brakes, stainless brake lines all the way around. Tyhe garage is going to check my work, align, and figure out the engine troubles. Damn was it great to drive that sucker after a year and a half!
    "I'm not a complete idiot - some pieces are still missing "

    98 GT ragtop 5-speed in Chrome Yellow - mine
    98 GT ragtop auto in Pink - wife's

  9. #9



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    Checked with the shop. Brakes had air in the lines, now good. Found minor vacuuum leak at base of plenum - my bad for not replacing the gasket when I put on the Accufab - new one on order. Thursday it should be ready. Gotta find a cruise this weekend!
    "I'm not a complete idiot - some pieces are still missing "

    98 GT ragtop 5-speed in Chrome Yellow - mine
    98 GT ragtop auto in Pink - wife's

  10. #10



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    Good news - vacuum leak was found, turns out the idiot who replaced the throttle body (me!) bent the gasket when installing it. Runs great now. Bad news - I told the mechanic there was a vibration in the drivetrain when I limped it in. Well, they decided to test drive it before checking the suspension and the rear U joint gave way. Good news - it was four houses down the street. Bad news - had to pay for a tow. Good news - two neighbors I had never met came out to see if I needed help, and after I had sat a while in the sun one came out with some cold water. Renewed my faith in mankind. The other showed me his aqua 57 Chevy hardtop with built small block, four speed, and Cragars, and complimented me on my Mustang.
    Last edited by PinkieT; Today at 02:34 PM.
    "I'm not a complete idiot - some pieces are still missing "

    98 GT ragtop 5-speed in Chrome Yellow - mine
    98 GT ragtop auto in Pink - wife's

 

 

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