Plugs or Coil Pack or O2 or combo?

Discussion in '3rd Gen - 2007 - 2017' started by Denethor, Feb 11, 2019.

  1. Denethor

    Denethor Full Access Members

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    It's probably getting time to change the plugs anyway, but let me throw out there the symptoms and get a consensus from the masses on here.
    Regular fuel regardless of octane, I've tried tanks of 87-93. Under hard acceleration I get #8 cyl mis-fire code and sometimes #3 but rarely.
    If I run Flex Fuel and keep the tank 51% or more Ethanol, no mis-fires what so ever BUT when idling in traffic for long periods or just idling in park, i get a check engine light for catalytic converter out of range (I assume this is due to the alcohol burning so clean there is not enough difference from front O2 sensor to the rear one??). On the OBDC the cats do run very cool on flex fuel vs pump gas.
    Last year I had the very common issue where the heater hose gets a leak in that T connector so the COPS got soaked and might have been damaged.
    Ford mechanic friend said don't replace the COPS unless you know they are bad because a good portion of new ones are DOA. Another local mechanic said do both while you have them out.

    Any thoughts on why no mis-fires on Flex and why Flex causes Cat issues?
    Any way to ensure a COP is good?

    Thank you.

    Also MPG suffers GREATLY with Flex making the cost savings not worth it.
     
  2. JExpedition07

    JExpedition07 Full Access Members

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    If you had the heater t-connector leak soaking plug wells it not only wrecks coils but damages plug performance as well.
     
  3. 1955moose

    1955moose Full Access Members

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    There's 2 ways to check a coil. One is pull it, get out your volt/ohm meter, and measure both primary and secondary resistance. Specs online. Second way is swap suspect bad coil to cylinder next to it, if misfire code moves, bad coil. That leaking hose shorted out #8 coil. You can buy a set of the Accel or other sets of 8 coils, keep a few of the old Ford ones around in case of failure of new one. Or buy a set of Motorcraft ones for around $70.00 for set, save a few. As far as your cat, you'll need to run fuel trims, and determine if it's a cat, a vacuum leak, or bad 02 sensor. Don't know why the alternative fuel works better than gas, maybe the octane, or whatever's in it, fools the cats and computer.

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  4. Denethor

    Denethor Full Access Members

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    The heater hose leak was over a year ago, and its on the odd number side of the engine, so it "could" explain the random #3 but not the rest.
     
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  5. JExpedition07

    JExpedition07 Full Access Members

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    Very true, I’m sure others will chime in. In my experience when I get a specific misfire I replace everything spark related on that cylinder. Most view this as a waste and diagnose more.
     
  6. 1955moose

    1955moose Full Access Members

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    Their is no odd side as the driver's side is 5,6,7,8. Your thinking of GM products . You didn't say where the coolant leak was, I took a shot. Coolant leaks can get under the cop plug, and never go away. My advice is to pull all the plug connectors and spray them out with electrical cleaner. Do the same with boots on each. A simple bit of coolant in there, will have you chasing your tail for weeks trying to get rid of miss. Same goes for any corrosion if not cleaned up. Electricity needs a clear path, or resistance builds up, and current can't flow. Same goes for battery, pull terminals wire brush both ends, put a barrier after. You'll get it fixed.

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  7. Denethor

    Denethor Full Access Members

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    Yes, sorry, I mis-spoke, I meant the even cyl8 side is opposite the hose that always leaks at the T connector but the odd Cyl3 was right near the leak. I'll do some testing on the cops when it warms up a little outside.
     
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  8. 1955moose

    1955moose Full Access Members

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    No worries. The boot or spark plug may be your problem on #8. If #3 got wet, then your probably sunk on that coil. Try cleaning and testing both before buying a new one. The original Ford coils are pretty tough. On most coils 1-2 thousand ohms for primary test, and 8-11 thousand on secondary side. Best bet, test one of known good ones, compare to suspect bad one. Easiest way to know if a parts good.

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  9. TobyU

    TobyU Full Access Members

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    As Moose said, pull them out (an might as well do plugs if you sad it needs it) Blow out the plug wells with compressed air really well. Replace the rubber boots and make sure the springs inside them are dry. Then reinstall. I would put #8 in one of the easy to get to front positions 1,2,5, or 6 then see if all is well or if you miss moves.

    I am a fan of the $30 sets of ebay coils because I have had good luck so far with them. I do however keep a box full of oem and often like new replacements I pull out of fords though.
     
  10. Adieu

    Adieu Full Access Members

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    It's not even-odd

    It's 1-2-3-4 front to back passenger side, 5-6-7-8 front to back driver side

    Most obvious place for heater hoses to mess things up is COPS #2 & #3, but who knows


    #8 (driver side, closest to driver) could ostensibly get flooded while topping off coolant or something
     

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