04 Gt Rough Idle. Out Of Ideas...

Discussion in 'SN95 4.6L Mustang Tech' started by richy28510, May 25, 2013.

  1. richy28510

    richy28510 New Member

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    I recently pusrchased a 04 stang. After a few days it developed a slight rough idle. It has gotten worse and worse, but does not throw a code. I've replaced plugs, air filter, fuel filter, pcv valve, upstream 02 sensors. . I cleaned the throttle body and injectors. I unplugged the maf while it was runnng and idle smoothed out and it ran amazing. So I figured maf was bad got new one installed and same thing. I reset the computer a few times. Nothing is fixing this rough idle any suggestions???
    04 ,72k miles.
     
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  2. COramprat

    COramprat Drone Driver
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    Check the fuel rail pressure sensor. You can pull the vacuum line off and if it squirts fuel at you, then it is bad.

    [​IMG]

    Look toward the firewall on the drivers side.
     
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  3. richy28510

    richy28510 New Member

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    I will check it. Thanks
     
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  4. Mattstang04

    Mattstang04 Active Member

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    You may want to check your idle air control valve. When my idle got rough, I replaced it and it took care of the problem. It is a fairly common problem with Mustangs.
     
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  5. richy28510

    richy28510 New Member

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    Tnyway to test if it id bad?
     
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  6. richy28510

    richy28510 New Member

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    Stupid tablet...Anyway to test it?
     
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  7. COramprat

    COramprat Drone Driver
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    I think there is a voltage test. It's in a Chilton's. Go get one...best 25 bucks I ever spent.

    Generally with a bad IAC the car will not run without mashing the gas. Keeping the RPM's up will allow it to run but as soon as you let off the car will die. I've never heard of any rough running issues with the IAC but that doesn't mean it doesn't happen.

    The Fuel Rail sensor is an easy one. Once you pull the vacuum line you will know it there is a problem.
     
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  8. richy28510

    richy28510 New Member

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    Check the fuel rail sensor working properly.
     
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  9. richy28510

    richy28510 New Member

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    Hopefully when I get my sct itsx tuner Monday I can map the idle to see whats going on.
     
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  10. COramprat

    COramprat Drone Driver
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    It may tell you something, then it may not. Is it throwing any codes?
     
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  11. richy28510

    richy28510 New Member

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    No codes
     
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  12. COramprat

    COramprat Drone Driver
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    Might be a vacuum leak. Check all the lines and hoses for cracks.
     
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  13. Rusty67

    Rusty67 Well-Known Member

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    If you can have the ECU read for TIDs you might find something useful. My dad's Mustang had issues and I found it was failing TIDs relating to the DPFE but it wasn't throwing codes. I checked and the DPFE hoses were bad and causing a vacuum leak. Car idles great now. Not saying that is your problem.

    As far as the IAC is concerned, it wouldn't hurt to yank it out and clean it.

    If you are worried about a vacuum leak you can take it to a mechanic and pay for a smoke test.
     
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  14. richy28510

    richy28510 New Member

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    Just installed my tuner and ran it and blam at 80 it broke up and threw a code. Bad coil. But I think I have more issues than that. Will check vacuum lines
     
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  15. richy28510

    richy28510 New Member

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    Found out car sat up for 3 years.
     
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  16. Rusty67

    Rusty67 Well-Known Member

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    The TIDs would have told you about a missfire on the cylinder without it throwing a code. You may or may not have a bad coil. Could also be the spark plug or the injector. Move the coil pack to another cylinder and read the TIDs after you have the issue again. You should see the missfire count in the TID follow the coil pack. If not you have another problem.
     
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  17. richy28510

    richy28510 New Member

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    Somehow the coil connector unplugged itself . Replugged and it sounded like it (normal self) ses light went off. I will have the car at the shop tomorrow to test your idea.
     
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