#4 Cylinder and Gummy Plug - Pic included

Discussion in 'Fox 5.0 Mustang Tech' started by bretamo, Sep 22, 2006.

  1. Car seemed to be missing and I ran a cylinder test where #4 came up as a problem. I pulled the plug and its all gummy.

    No other codes turned up on my code reader.

    See photo below of gummy #4 and a clean #3.

    This plug was pulled after about 4500 miles of city driving, and after upgrades including GT-40 heads, Comp Cam studs, rocker arms and pushrods, Cobra Intake and 65mm TB.

    What concerns would you take away from this?

    Thanks for any advice.

    View attachment 438909
  2. Looks like your burning a lot of oil in that cylinder or the plug is bad and was not firing? Perform a compression check on that cylinder to confirm bad rings, leaking head gasket. Did you put any sealer on the intake side rocker arm studs?
  3. Thanks - ARP sealer was indeed used with installing the Comp Cam studs.
  4. how does the #8 cyl spark plug look? what mods have you done if any
  5. rings=toast.
  6. Ohhh noooo! I like my rings all and I don't like toast.

    The #8 plug looks normal. But I have to ask, what if it was similar? What coorelation would you make for the back two plugs getting gummed up?

    My recent mods were in the first post; the plug was pulled after about 4500 miles of city driving, and after upgrades including GT-40 heads, Comp Cam studs, 1.60 rocker arms, pushrods, Cobra Intake and 65mm TB.
  7. IF the #8 was similar, there would be a good chance you are sucking oil from the pcv valve into the intake,
    on a stock intake the pcv is shielded, that shield needs to be transfered to the new intake, otherwise oil in the lifter valley will find its way to the back where it will be pull up by the vacuum of the intake... being that the #4 & #8 runners are the closest to the pcv, they would have the most oil build up.
    I ran into this problem when I installed my trick flow intake.:shrug:
  8. That's just too much build up on that plug for there not to be a critical issue internally...wether it be an internal coolant leak, blowby, or other.
  9. Thanks for the info, Powertraks. I'll check the PVC and intake - but I am pretty sure I got the screen in right when I installed the new intake.

    As FYI, I cleaned up the plug and reinstalled and the motor has been running pretty good for about 50 miles so far this weekend. No smoke, no odors, no external signs of trouble.

    However, I don't have high hopes and am thinking I need to prepare to pull the motor and have it worked over. Gonna look at the PepBoys add for a jack and motor stand after the football games.
  10. do you still have your old intake?
  11. you'll be amazed how much build up you can get in only 2 weeks time
  12. This is kinda random, but when you go to buy a jack, don't buy the cheap one, buy a decent one with the larger lifting pad.

    For the engine stand, if you have the option of buying a 4-wheeled one instead of a 3-wheeled one, do it. They are more stable.

  13. Are you working on a Flat head Ford or what? :rolleyes:

    That kind of build up is not normal, and not good. :nonono:

    Also, a pcv issue will build oil deposits on ALL plugs, not just one or 2 of them.

    I doubt the problem is pcv related.

    I also doubt the rings are bad in that cylinder. That blowby would cause issues with crankcase pressure venting out of the pcv. Excessive pressure venting from the pcv = Oil contamination in the intake manifold = ALL plugs will be oily.

    Leaking valve seals would tend to leave oil in the intake as well. There is always a vac source in the intake, so oil leaking through a valve seal would quickly spread to the rest of the intake.
    I doubt the problem is valve seal related due to how clean the other plug is.

    I would first look at the spark plug wires. With the use of dielectric grease, sometimes the wires will not seat properly on the plug.
    A plug that does not fire (or fires weakly) will build up some nasty goo pretty quick.

  14. I'm looking at the bright side after VRSTANG's post because the plug was indeed not firing for the last week. The car has felt like it was missing for the last two weeks, and I just ran the cylinder test on Friday.

    So its the chicken-or-the-egg situation; did the build up on the plug stop the firing, or did the plug not firing cause the build up?

    I am sure hoping that it is the plug not firing that caused that build up!

    Well, thanks everyone - I'm going to get busy in the garage after the first round of football games this Sunday.