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Spark Plug

Thread in 'Performance' started by Art G, Dec 8, 2010.

  1. Art G

    Art G Active Member 1st Gen Owner V6 Engine

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    Greetings. Maybe someone can help me out here. I changed the original motorcraft spark plug when my 05 ST turned 100,000 miles. Now I have put 4,000 mile on the new Autolite Double Platinum APP103 plugs. I noticed a poor gas mileage and sometimes it hesitates on acceleration. I did not notice this when I had the old plugs in them. Any advice is appreciated.

    BTW, when I removed the old plugs the gaps were about .085 all around. I gapped the new plugs to .055.

    Thanks
     
  2. Tom Schindler

    Tom Schindler Well-Known Member 1st Gen Owner V6 Engine

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    Personally, I never use anything but OE plugs. Some members use other gimmick plugs and claim they are awesome.



    I am too lazy to do the job twice.



    It is either the plugs or it has been colder in your area and that could be the drop in mileage.



    Personally, I would swap out the plugs for Motorcraft plugs and be done with it. Then write it down as a lesson learned.





    Tom
     
  3. Robert Caffyn

    Robert Caffyn Well-Known Member 2nd Gen Owner V8 Engine

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    Is it possible you have too much gap in the plugs? Check your owners manual for the specs, I sorta thought it was around .44-.45 Bob
     
  4. scott degroot

    scott degroot Well-Known Member 2nd Gen Owner V8 Engine

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    More than likely when you replaced the plugs you inadvertantly damaged one of the spark plug wires and it is this that is causing your hesitation(misfire) which in turn is hurting your mpg. I would bet that replacing the spark plug wires would solve your issues and FWIW you should be just fine with those plugs. I don't have specs in front of me but I think just about every Ford truck motor runs the spark plug gap at .052-.056 inches
     
  5. Art G

    Art G Active Member 1st Gen Owner V6 Engine

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    Thank you for all the response.

    I gapped the new plugs .055" just within the required specs as called for in the owners manual .052-.056. Yeah I hate to do things twice specially taking off the passenger side plugs. I thought there might be somebody out there that has used the same Autolite plugs.

    Maybe I check the plug wires, maybe its due for replacement.
     
  6. scott degroot

    scott degroot Well-Known Member 2nd Gen Owner V8 Engine

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    I guarantee you that unless you crakced a plug putting it in the plugs ARE NOT YOUR PROBLEM. Fords are very picky when it comes to plug wires and there is a better than average chance that you messed them up when changing the plugs I've seen it happen countless times
     
  7. John Ratajczak

    John Ratajczak Member 1st Gen Owner V6 Engine

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    I had the same problem when I changed my plugs. I found out that I cracked the #5 plug. So I changed the plug & still had the same problem. Turns out running with the cracked plug left a carbon track in the plug boot. Cleaned out the boot and it runs fine now. So if you find that you cracked a plug clean out the boot.
     
  8. scott degroot

    scott degroot Well-Known Member 2nd Gen Owner V8 Engine

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    If you have carbon tracking in the boot then repalce the wires, the point where the carbon tracking was is now a weak point
     
  9. Jerry G.

    Jerry G. Member

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    If I read correctly he said it was doing the same thing with the old plugs . hesitation when taking off could also be a dirty MAF sensor . Just my 2 cents .
     

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