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4.6 XLT 2003 P0306 and P0316 help!!!!

Discussion in 'Stock 2002 - 2005 Explorers' started by ronixd, May 31, 2017.

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  1. ronixd

    ronixd New Member

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    My 4.6 XLT 2003 has codes p0306 and a p0316.


    I have put on a new dorman intake manifold, new motorcraft plugs, new cop boots.

    I have moved the cops and fuel injectors around but the misfire stays in cylinder 6. Pulled all plugs and all look good.

    Compression for 1-4 is 190psi, 5-8 170psi. I hooked up a vacuum gauge to the brake booster vacuum line, upon cold start up gauge starts at 180inhg then immediately drops to 140inhg for around 4-6 seconds then climbs back to 180inhg and steadily stays there as it should. this only happens during a cold start or after the engine being off for around 30 min. I could post a video of the vacuum gauge but I don't know how.


    I am baffled and need help!
     
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  3. Number4

    Number4 "I'm counting to 3, then I'm getting your dad." Elite Explorer

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    Test the wiring to #6 injector and coil.
     
  4. ronixd

    ronixd New Member

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    put a noid light on cop wiring and they look all uniform to me. have not tested injector wiring yet. any suggestions on how to go about it?
     
  5. ronixd

    ronixd New Member

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  6. ronixd

    ronixd New Member

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    Replaced both cylinder 6 lash adjusters. Still have P0306 and P0316!
     
  7. ronixd

    ronixd New Member

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    Update, i replaced the broken fuel injector and cop clips and the camshaft sensor. Still have p0306 and p0316 codes!! Help!!
     
  8. Number4

    Number4 "I'm counting to 3, then I'm getting your dad." Elite Explorer

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    Safe to assume you cleared the codes after each repair?
     
  9. ronixd

    ronixd New Member

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    Hi, i usually drive the car a few days for a couple of hundred miles to see if the code goes away, if it does not, I manually clear it.
     
    Last edited: July 17, 2017
  10. Drewmcg

    Drewmcg Elite Explorer

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    You might try slipping off the two-wire clip for the Crankcase Position Sensor, spraying the harness (female) and CPS with electronic cleaner, and using some dielectric grease on the harness before putting it back on.

    I don't know the 4.6, but you might try removing the (new) plug from #6 and swapping with another cylinder. Reason: you could have cracked the porcelain on the new #6 plug when installing. By swapping it, if the misfire stays only in #6 you will have truly eliminated the plug as an issue.
     
  11. Drewmcg

    Drewmcg Elite Explorer

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    Also... you probably saw this, but sidziner had luck replacing all 8 COPs with a cheap set he bought on Amazon ($33 for the entire set !--see his thread). How old are the COPs?
     
  12. ronixd

    ronixd New Member

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    Thank you for the reply. Yes i have moved the plugs around, i also replaced the camshaft sensor. Cleaned all connectors and used dielectric grease when reinstalling. cleared the codes and the p0306 and p0316 always comes back after a couple of start ups. And yes i saw the sidzingers post, and i ordered the set he recommended and installed it. I thought it solved the problem!!! But i was so bummed out when the code came back after a week of regular driving.
     
  13. ROBinGa

    ROBinGa Active Member

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    Did you say you have changed the plug itself? One other thing, can you inspect the wire and connector that connects to the COP to make sure nothing is nicked or corroded in the connector? If possible trace that wiring for cylinder 6 as far back as possible in the wire loom for a nick in the insulation or kink or something. If it's always cylinder 6 then it has to be something like that if you are swapping COPs and other components but misfire is always 6
     
  14. ronixd

    ronixd New Member

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    Yes new plugs all around. I also replaced the bad connectors. Yes i replaced the camshaft sensor. Will follow your advise on the wire loom/harness inspection. Thanks. Anymore advise is very much welcome keep them coming!!!!!
     

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