Diagnosis Unknown

Discussion in '2005 - 2009 Specific Tech' started by jeffbrown328, May 18, 2013.

  1. I have a 2006 mustang gt with 125k miles on it. In Jan it threw a random misfire code P0300, so I changed out all 8 of the spark plugs. I thought it was bout time. About a month ago I threw a P0301 so I replaced the coil pack, which appeared burnt on the coil end, on cylinder 1. Seemed to fix that issue but a week later I threw P0303. I tried a new coil pack, which also appeared burnt on the end, but it still says cylinder 3 is misfiring. I also replaced the fuel injector. Every 80 miles or so the check engine light will go on solid, and the scan will come back as P0303. I checked the compression and all cylinders are normal. No intake leaks. There is a slight ticking sound noticeable at idle so I flushed the engine and changed oil to see if it was the lifters or valves sticking...no luck. Still ticking slightly and throwing the P0303 code every 2 days or so. Car runs great, its not an easy misfire to feel but i believe the computer. I just am at a loss and have no idea where to go from here?
  2. But wouldn't that throw its own sensor? My fuel trims are a little heavy on the lean side, but equal on both banks. Long fuel trim is usually running 8-9% lean on both banks, short fuel trim is at 0% plus or minus 1-1.5%.

    Would it this help rule out or indicate 02 sensor problem?
  3. With 125K miles, thought an 02 might be on its last legs.

    The misfire on cylinder 3 is basically saying that cylinder is lacking combustion. Re-reading your original post, with regard to the ticking, I am wondering if the injector on cylinder 3 is acting up? At idle, you can unplug the injector harness to see if the ticking goes away or not.
  4. I removed the wire harness to the injector in cylinder 3. The slight ticking didn't go away or get worse. What does that mean?

    Also, no light was on but the computer had thrown P0353 code. Maybe the coil pack I replaced was defective. Ill reset and see if it comes up again before I return it and try another.
  5. You can alwsys move that coil pack to another cylinder and see of the code changes.
  6. P0303 went on again. I'll move the coil pack tomorrow and see if it follows it or not. Thanks for the help and ill update you on the results
  7. Does the fact it takes a day or two of driving for the light to go on mean anything? Also the light never flashes, it always goes on solid.
  8. Try to remove the coil plug one at time to see which coil, when removed, stop the ticking. I suppose it's one of the coils that is misfiring somewhere. It can happen if there is dirt or the coil rubber is damaged.
  9. I think I figured it out. Today the spark plug on cylinder 3 shot out and tore off the bolt holding the coil pack. It probably wasn't torqued correctly and finally came loose enough to be ejected. Checked the rest and they were correctly torqued. Threading was still good, screwed it back on and attached the coil pack, minus the bolt :) Drove it 80 miles and ran perfect. No trouble code yet, not even pending, but I'll let you know.

    Now the ticking is extremely light. I can't hear it with the window up. Also can't hear it with the windows down unless I'm next to a car or wall.

    I have replaced 2 of the 8 coils, I have a specific code for the coils.

    So Alien, you think the coils have internal parts that can fail? Should I just look for physical damage to the coil and boot or just replace the remaining 6? I guess im just afraid pulling 1 at a time might not work if more than 1 is bad.
  10. it's really hard to see a physical damage on these coils. they are static charge coils, powerful but it's not easy to send the spark to the plug instead of somewhere else.

    The spark happens where the best condition occurs; usually is on the spark plug because of the right distance between body and electrode but, in certain engine load condition, the dielectric potential inside the combustion chamber is not so 'friendly' and the electricity from the coil can find a better path where to go. dust, small cracks on the coil body or worn rubber insulator can help this phenomenon. The problem is that once the electricity finds a 'path', the damage will be worse and that coil will be useless. I didn't find yet a best fix to restore the insulation in these cases; it worked for few months and restarted again.

    even if it's more than one, if you exclude a bad coil, the ticking should be anyway less; the spark ticking is very tipical, high frequency, different than the injector one.
  11. Any updates?