Misfire codes, but can't feel a misfire

Discussion in '96-04 - 2V Specific' started by Spyder328, Aug 14, 2016.

  1. Spyder328

    Spyder328 New Member

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    So my 2004 GT (4.6 v8, 5 speed manual) is sending some misfire codes (P0300, P0304, P0306) but I don't feel any misses anywhere. I changed the fuel filter (used a Motorcraft), changed the plugs (motorcraft), and coils. Also bought some MAF cleaner and cleaned the MAF sensor and ran a full tank of gas thru it that had injector cleaner added to it. I put about 70 miles on it (after disconnecting the battery) then the check engine light came on [​IMG] I got the codes read and I had P0300, P0304, and P0306. Before I did the filter, plugs, coils, injector cleaner, and MAF sensor cleaner I had codes P0300, P0302, P0304, P0306, P0307, P0308. I drove it twice after the light came on then, where as this time I went right to get it read. I'm wondering if more codes would have shown up if I had driven it a little longer like last time. It still has a slight pop every now and then on idle and it feels like a slight stumble. I can run it on 5th gear at 40mph and its smooth and it pulls strong. All the plugs that came out looked like it is running lean. I don't have a scanner or anything to check what the fuel pressure is reading. I'm starting to wonder if there is a tune in it that I don't know of and it is causing issues. I have high flow cats, x pipe, slp loudmouth resonators, 2.5" exhaust, intake, aftermarket clutch, and under drive pulleys. I'm unaware of anything else that has been done to it as this was a recent purchase. Also worth mentioning, the hole on my intake for the air temp sensor is plugged and I can't find the wires for the sensor anywhere, I also notice I have pink injectors. I have read that the GTs came with pink or orange injectors and I am curious to why some apparently have pink and some have orange. Thanks
     
  2. Nighttrain

    Nighttrain Well-Known Member

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    First off id get rid of the underdrive pulleys. Some people dont have a problem with tgem but they put added strain on your accessories as well as causing your car to run hotter especially at idle. On to your issue. You shouldnt need a scanner or tuner to see what your fuel pressure is. There is a shrader valve on the fuel rail. You can pick up a gauge at autozone or advanced auto pretty cheap or even make your own. Screw it onto the valve and turn the key on, dont start the car. When you turn the key to on, the fuel pump kicks on for a prime cycle then shuts off. Get your reading and write it down. Then start your car. While running get a reading. Then use the throttle body to rev it and hold it to about 2500-3000 rpms and see if you have alot of fluctuation. Im going to go out on a short limb and say its either your fuel pressure regulator, or pump. Check your fuel filter again and see if it has any crap in it after running the tank you have. You can get an adjustable fuel pressure regulator for fairly cheap. Thats what id do.
    Most tunes increase your timing and fuel to the motor. If it does have a tune you wouldnt read your plugs as lean unless youre shorting the motor of fuel.
     
  3. Spyder328

    Spyder328 New Member

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    Thanks for the reply, it has no issues running hot, I have sat in it at work with the A/C on for an hour in 90 degree weather and it has been fine. The charging system seems strong and the A/C works great. As for the shrader valve, my fuel rails don't have one. They look stock but they don't have a valve (was looking for it when I did the fuel filter)
     
  4. Nighttrain

    Nighttrain Well-Known Member

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    As far as i know, 04 still had them.....pics? That might help. I still think its fuel tbh. Where in pa are you?
     
  5. Frank.JD.Perez

    Frank.JD.Perez Well-Known Member

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    if you changed all the spark plugs then i guess i would start to wonder if your cops are needing replacing...a few of us here like ballistic and white95 (as well as myself) were having some missing issues, but we have coil packs and mine was solved with (i think main culprit among other changed parts) changing out the bad spark plug. if you havent looked at those guys (cops) yet i would start to look at them, but im pretty sure nighttrain already gave you a solid lead.
     
  6. Frank.JD.Perez

    Frank.JD.Perez Well-Known Member

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    also nice avatar lol
     
  7. Spyder328

    Spyder328 New Member

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    I'll take pics tomorrow, I have seen pictures of where the shrader valve is supposed to be, but there is nothing there on mine. And I'm like 10 minutes from Parksburg.

    I replaced all the cops when I did the plugs

    lol thanks :cool:
     
  8. Nighttrain

    Nighttrain Well-Known Member

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    Yea im about ten min from parksburg too.

    If i remember correctly it should be on the driver side. The driver side is the feed side, unless they changed it for an 04.
     
  9. SOHC_Foodblister

    SOHC_Foodblister Member

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    Your issue sounds fuel related. Post a pic of your fuel rail so we can confirm you're not overlooking the schrader valve. The fact that you had misfires on 5 different cylinders, leads me to rule out bad injector(s). As Nighttrain said an FPR or fuel pump jump up as likely culprits. You need to find a way to measure fuel pressure and go from there.
     
  10. Nighttrain

    Nighttrain Well-Known Member

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    I looked up 04 fuel rails on the google. All the stock rails show one right by the feed tube. Oddly though some show the feed on the passenger and driver side. All the aftermarket feed rails dont show one unless they are under the fancy covers.
     
  11. Spyder328

    Spyder328 New Member

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    Here are some pictures I just took of the fuel rails. I still can't find the shrader valve :confused:

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
  12. Frank.JD.Perez

    Frank.JD.Perez Well-Known Member

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    Huh...interesting...it should be on the end of the driver side fuel rails closest to the front...
     
  13. Nighttrain

    Nighttrain Well-Known Member

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    @Spider328 check by the feed line on the the driverside, and the crossover tube on the driver and passenger side.
    Also wouldnt hurt to pop the intake tube off, just in case its under there. All the pics i saw of them off a motor showed it by the feed line though.
     
  14. Spyder328

    Spyder328 New Member

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    I had the intake off when I was looking for it a few days ago and still couldn't find it
     
  15. Nighttrain

    Nighttrain Well-Known Member

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    Did you check by your fpr/ feed line and crossover tube?
     
  16. Spyder328

    Spyder328 New Member

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    Yeah, but still nothing. So I ended up getting
    a UPR fuel rail adapter and put a fuel pressure gauge on it and a schrader valve. When I turn the key to prime the system it says I've got 38 psi, when running at idle it has 26 psi, and when I wack the throttle it jumps up to 40 psi. Does that sound about right?
     
  17. Nighttrain

    Nighttrain Well-Known Member

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    Your pump is getting weak, stock fuel pressure should be 35-65 lbs. So at idle it shouldnt drop below 35lbs. You said you already changed the fuel filter so that takes that out of the equation. Imo it wouldnt hurt to put an adjustable fpr on also.
     
  18. Nighttrain

    Nighttrain Well-Known Member

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    When a pump starts to go it gets hot causing the fuel to foam causing a lean event. Your injectors should be ok although orange connectors came in a crown vic(i think), pink were in something else idk what, 2v gt 19 lb injectors were black and yellow. 4v cobra 24 lb injectors were green (again i think, most of the 4.6 injectors are or were interchangable)
     
  19. Spyder328

    Spyder328 New Member

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    Yesterday I regaped the plugs (tighter gap) and reset the PCM then drove it a little. Nothing changed but I noticed that my fuel pressure is now reading 38-40 psi at idle :confused:
     
  20. Nighttrain

    Nighttrain Well-Known Member

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    Whats it read under load at wot?