P0302 CEL

Discussion in '2011+ Mustang GT 5.0L Tech' started by Riptide, May 21, 2022.

  1. Riptide

    Riptide Will work for Mustang.

    5,248
    17
    Car recently developed a miss and eventually threw this CEL.
    Info on the car:
    Replacing the coil pack on cylinder 2 did not resolve the issue. I pulled the plug. The plug was fouled with significant carbon buildup. There was oil on the spark plug threads but no oil visible on the tip or electrode. After replacing the plug the car ran normally.

    Today I removed the other 7 plugs. All 7 had the same issues with oil on the plug threads to varying degrees. There is also a lot of carbon buildup on the piston crown visible through the plug well. A couple cylinders aren't that bad but the others are pretty caked up with it.

    The car does not produce any obvious smoke to the eye. It doesn't consume oil either.

    The oil on the plug threads is a mystery to me. It doesn't appear to be leaking down the well from above. If the rings were shot I would expect the car to be smoking. And all the carbon buildup, also a bit puzzling, makes me wonder if it's running rich.

    Thoughts?
     
  2. redfirepearlgt

    redfirepearlgt forum member

    2,297
    144
    IT is common practice to should replace FI setup plugs on an annual basis. They are seeing on average 140%+ minimum at WOT than the stock setup which would pull little more than 85% fill at WOT. More air, more fuel, equals more burn. So plugs won't last as long. Second the gap is at a much smaller value (usually 0.026" to 0.030") on most FI setups. So they will also foul sooner. Most people replace annually or at about 10K with FI setups especially one running the boost level you are at. Contact VMP and give them this information and they will likely concur. This is all assuming the car does not have 100K on the OD, and has a good oil catch can setup on it.

    Datalog the car and see what the AFR is running or send it to Justin and ask. That is what they are for. Good people down there. NO reason to go to a bunch of us novice hacks for direction when you have professionals like VMP in your back court.
     
  3. Riptide

    Riptide Will work for Mustang.

    5,248
    17
    I'll call VMP next week.

    There is no catch can installed. I am running breathers on the valve covers and an oil cap breather. There is also no excess output on those breathers either. The driver side generally stays dry and the passenger side tends to see some oil seep through the filter media.

    I don't baby the car 24/7 365 but I do generally drive it pretty conservatively.
     
  4. redfirepearlgt

    redfirepearlgt forum member

    2,297
    144
    Good. You can eliminate oil migration. It is common to see especially on FI setups that don't have a passenger side oil catch system or at least breathers like yours. I suggest staying on top of the plugs. I generally replace plugs every 12-18 as I only put about 4-5K a year on them. There will always be a small amount of oil get past the rings and oil wiper into the combustion chamber. The amount you are seeing that has collected on those plugs in 18000 miles would likely equate to about 2 drops at most if collected I am guessing. With no oil loss to speak of - though you also do lose oil through those breathers though again it is minimal - all you are dealing with is not properly maintaining the plugs with regard to running an FI setup IMHO. Again if in doubt ask Justin or Joe or one of the newer tuners at VMP.
     
  5. Riptide

    Riptide Will work for Mustang.

    5,248
    17
    [email protected] got back to me today.

    Per their tech, this sounds pretty normal to them. I'll be changing plugs more often moving forward and will probably switch over to NGK on the next change. The oil on the plug threads is caused by blowby (they recommended a catch can, though I already have breathers) and the carbon buildup is nothing out of the ordinary.

    Regarding that carbon buildup. I'm now looking around at the best cleaner I can try in there and thinking of taking the car out for a 70-80 mile highway trip to see if I can get some of that buildup out of there.
     
    redfirepearlgt likes this.
  6. Tim Burns

    Tim Burns Junior Member

    2
    0
    I use sea foam and let it pull a full bottle through a vacuum line on a warm engine into the intake and let it set for 20-30 minutes. Crank it up and drive for about 10 minutes and you will not believe the amount of carbon that you will see come out. Your neighbors will think your car is on fire lol. you will see the smoke will turn from white to black and that will show you that carbon is being removed. It may throw a CEL but it will go off in a few minutes. Some will say this is bad for the cats but I generally only do it every 20 thousand miles or so.
     
  7. redfirepearlgt

    redfirepearlgt forum member

    2,297
    144
    There you go. Their tune...use their recommendations.
     
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.