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

Discussion in 'General Tech' started by PinkieT, Sep 13, 2018.

  1. PinkieT

    PinkieT Well-Known Member

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    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?
     
  2. 01yellercobra

    01yellercobra Well-Known Member

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

    ttocs Well-Known Member

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    replace the gas or was that a year old as well?
     
  4. PinkieT

    PinkieT Well-Known Member

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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...
     
  5. Silver95bird

    Silver95bird Well-Known Member

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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. 96blak54

    96blak54 Well-Known Member

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    Sounds like a tps fail. Try unpluging things one at a time to see if there is an improvement.
     
  7. ttocs

    ttocs Well-Known Member

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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.
     
  8. PinkieT

    PinkieT Well-Known Member

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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!
     
  9. PinkieT

    PinkieT Well-Known Member

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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!
     
  10. PinkieT

    PinkieT Well-Known Member

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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.
     
    Tillerman77 likes this.
  11. PinkieT

    PinkieT Well-Known Member

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    Driveshaft has too many dents and creases to be safe. Tomorrow morning I check on a local rebuilder, and if the prices is high will just go to Summit and spring for an aluminum Ford Racing piece. Yep, more money I really didn't want to spend!
     
  12. ttocs

    ttocs Well-Known Member

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    dents and creases? What have you been doing trying to better the dukes of hazard jumps or something?
     
  13. PinkieT

    PinkieT Well-Known Member

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    Yeah, right! :) Got lucky on the driveshaft, tho, walked into a 15% off Summit brand parts sale at the Summit store. Got a Summit aluminum high performance driveshaft with yoke and flange for $75 less than having a local guy build one off my old yoke and flange out of steel or buying the Ford Racing part. I bet it is the same piece as the Ford Racing part, just private label. Yippee!
     
  14. PinkieT

    PinkieT Well-Known Member

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    Got it home today. Yay! Runs great. The shop said put 50 miles easy miles on it so the springs can settle then we do an alignment.
     
  15. ttocs

    ttocs Well-Known Member

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    take it easy? Oh heck no you know bo and luke duke would find a place with the bridge out to test it, no reason you shouldn't do the same(and get it on video)
     
  16. PinkieT

    PinkieT Well-Known Member

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    Yeah, baby! Now that I have 3.73s instead of 3.08s, I plan on dropping the clutch and smokin'!
     
  17. evilcw311

    evilcw311 Well-Known Member

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    Vid or it didn’t happen........
     
  18. PinkieT

    PinkieT Well-Known Member

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    Still gotta get some parts back on it. Been sick. Maybe Saturday???
     
  19. PinkieT

    PinkieT Well-Known Member

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    Sunny day, feeling better. Got the cowl and wipers on, fired it up, took a spin down the road. Heard a noise, pulled into my mechanic's, we found a brake line rubbing on the exhaust. Fixed it on the spot. Pulling out a guy on the porch of the house across the street yelled "Light'em up!". Being the good neighbor I am, I had to oblige! My mechanic told me of a cruise nearby so I went and pulled up next to another Mustang. He went nuts over my car. My wife surprised me by bringing her pink car for a while. Tomorrow, a good cleaning and more miles. :)
     
  20. Tillerman77

    Tillerman77 Well-Known Member

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    Glad it is back on the road PinkieT!