Need to adjust Idle on FRPP 70mm T/B!!! (ASAP)

Discussion in 'SN95 4.6L Mustang Tech' started by BlackenedSVT, Mar 11, 2006.


  1. SilverGTV8

    SilverGTV8 New Member

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    The throttle blade set screw is not the problem. By unplugging the IAC from the harness you are elminating the ECU control for idle and relying soley on the TB blade position.

    The car would do exaclty what yours did when you removed the IAC from the harness, idle down to the point of almost stalling. That means the TB blade position is correct.

    I wouldn't play with the TB blade set screw. It will not alter the idle.
  2. jstreet0204

    jstreet0204 Active Member

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    If your tps is now within range, and your throttle blade is closing, my guess it you've got a vacuum leak. somewhere. You can use a propane torch to find it.


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  3. SilverGTV8

    SilverGTV8 New Member

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    You might want to tell him how to use that :rolleyes:

    You can do the same thing with carb cleaner or brake clean. When the motor is cold and running, spray a small amount of either around any connection and listen for a change in idle. If it changes you have a leak. If it doesn't move on to the next one.
  4. BlackenedSVT

    BlackenedSVT Active Member

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    Hmm i'll try and give this a shot. And wouldn't you use propane for for a failing or misfiring piston/cylinder? Why or how would you use it for vacuum leaks?


    yeah the motor is still throwing the "vacuum leak" code. Think my ported intake has something to do with it?
  5. jstreet0204

    jstreet0204 Active Member

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    While the engine is running, pass the UNLIT torch over all vacuum lines, past the intake manifold gaskets, etc...should you pass the nozzle of the UNLIT torch near a vacuum leak, the idle speed of the engine will increase momentarily because the propane will be sucked in through the vacuum leak and burned as fuel inside the engine. Listen carefully for a rise in engine rpm's.
  6. BlackenedSVT

    BlackenedSVT Active Member

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    Yeah figured thats where you were going with that. So maybe i'll look into it this weekend when i have access to one at my shop.

    Also....what if there IS a vacuum leak?? put a clamp over the hose to seal it better?
  7. jstreet0204

    jstreet0204 Active Member

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    Depends on the leak, could be a gasket leak around the throttle body or plenum, or it could just be one of the small hoses wasn't hooked back up or came loose.
  8. BlackenedSVT

    BlackenedSVT Active Member

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    Well maybe i'll give it until this weekend to work itself out, then i'll be ripipng her apart again and starting over and seeing if i can find any problems
  9. BlackenedSVT

    BlackenedSVT Active Member

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    OK HERE IS AN UPDATE:

    I took the entire plenum and T/B off today, and re-installed everything, just to make sure all the gaskets were tight and everything was seated correctly. Upon starting the car up and letting idle for 15min, then restarting...the car STILL had the vacuum leak problem, high idle and hanging RPMS....

    oooook, so. I then disconnect the MAF sensor, then disconnect the air intake tube going to the throttle body. Then i started the car up, and since the MAF was disconnected, the car was still able to run, but ran rough.

    I then put my hand over the throttle body completely, and the car did NOT die. Confirming i do have a major vacuum leak. What a PITA!! :mad:

    Ok while i was taking the plenum off the uper intake, i noticed there was NO gasket there, just a blue O-Ring...is that normal? I'm trying to figure out WHAT gasket is causing the leak, and im thinking that it is the Throttle Body Gasket going to the Plenum. Because i re-used this gasket, and did not get a new one.

    I was NOT able to spray any carb cleaner or anything like that over any of the lines to check for the vacuum leak, i will do that this weekend when i have access to some and maybe a propain torch. In the mean time, i thought i would update you guys....
  10. hotdog71

    hotdog71 Member

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    Yes, the o-ring gasket is normal it's the only one under the plenum.
    Sounds like it's your TB to P gasket unless you have a crack in your plenum after it was ported, just a thought!
  11. BlackenedSVT

    BlackenedSVT Active Member

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    Nope no cracks in the plenum. So i'll try changing the T/B gasket later in the week, otherwise i dont know what to do lol
  12. BlackenedSVT

    BlackenedSVT Active Member

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    Anyone know where i can buy a gasket kit?

    I'd like to replace all the gaskets while im at it

    - EGR gasket
    - IAC Gasket
    - 70mm T/B Gasket to plenum.
  13. dustang50

    dustang50 Member

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    Go to Autozone & buy the gasket material - they sell rolls of it for $4. Then just trace & cut your own.
  14. BlackenedSVT

    BlackenedSVT Active Member

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    Just went to autozone and bought some Sea Foam and this gasket maker stuff. They didnt' have the cork gasket rolls, only the rubberized. Which will work fine i think. I'll get back to you guys
  15. a97mustang

    a97mustang New Member

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    drill 1/4 hole on blade !
  16. jstreet0204

    jstreet0204 Active Member

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    do not do this!! :nonono:
  17. BlackenedSVT

    BlackenedSVT Active Member

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    huh? :scratch: what does that even mean?
  18. Shiroelex

    Shiroelex There's nothing worse than aut Founding Member

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    I sure wouldn't be drilling that, personally.

    I'm beginning to think your problem may lie elsewhere. If you didn't hear a hissing or something when you put your hand over the throttle body when it was running, then there is a major problem somewhere. Unless, you didn't cover it completely. My hand gets sucked to the TB when I get about a centimeter away from it, and it holds on for a second, while the engine stalls completely. Your IAC can allow air in, but I wouldn't think enough to keep the car running with a completely blocked TB.

    I would check that IAC, the gasket it has mounting it, the EGR and it's gasket, and the upper plenum mounting gasket.

    Remove any mods like the IAC restrictor, whether it be the plate or the copper cap, and start it up.

    Make sure the two hoses running to the intake tube are connected, and that the clamps that hold it to the TB and to the MAF are snug.

    Make sure the IAT sensor is in place, and the MAF is plugged in.

    Look everything over, and make absolutely sure that there are no openings at all between that TB and the MAF.

    Start it up, and listen for where you hear the most wind noise. If the idle never drops, while it is running, go to town with carb cleaner. Spray everything shy of the COPs. If the spray doesn't change the idle in any way, then the problem isn't anything you did, it's a coincidence that happened elsewhere on your car. Try a little spray around the lower intake to head connection even. Hell, spray by the coolant crossover. Those hairline cracks can be hard to see on black plastic.

    Do you have a tune loaded, or a chip perhaps? Something may have been adjusted, because the last plenum may have had a defect that caused a low idle.

    Did you mess with the set screw that holds the new TB blade open at all? The blade should just come to complete close on it's own, and not stick at all. If it's held open at all, too much. If it closes too far and sticks a little when you try to move it, not open enough.

    Last thing I can even think of, is possibly the DPFE EGR pressure sensor. There may be something funky going on with that. You should try to get a good video of everything that is happening; maybe we can see something you do not.
  19. BlackenedSVT

    BlackenedSVT Active Member

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    IAT Sensor??? Or did u mean IAC?? Whats the IAT??


    Also, no i did not mess with the Set-screw. Although i am getting this T/B second hand from a friend that had it installed by La Roccas Performance down in south jersey...so i'd imagine they didn't mess with it either.

    And no i have no tunes installed on the car.

    And where/what is the COPS??

    I'll try and take a video tomorrow or the day after.
  20. Kilgore Trout

    Kilgore Trout Fried or Broiled ?

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    Just take it to a shop and be done with it.

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