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  • Underload detonation

    Crown Vic 103,000 miles (all freeway) CNG 4.6L Modular Engine - Just cleaned out the fuel lines, injectors replaced, coils replaced, plugs replaced all this but still getting a detonation (pinging) whenever adding load (acceleration). One tech is saying I need to tear down the engine ($900) to see what is wrong with the bottom end (wouldn't just checking the oil for metal particles be a better first step) and another tech is suggesting I decarbon the the valves ( which kinda makes sense since the carbon would tend to create an uncoodinated combustion process) with a chemical **ent (seafoam).

    What should the first step be ? Help !

  • #2
    Re: Underload detonation

    A couple other suggestion. Check the cylinder for carbon build up, use a borescope through the plug hole (a pain at best). You may have solved the carbon with the "seafoam", but it doesn't hurt to double check.

    Use a scantool to check sensor reading:
    ECT or air inlet temperature sensor reading lower than actual will allow more timing advance. Those readings should be the same after an 8 cold soak.

    MAF sensor can cause problems, check what altitude (BARO rading) the vehicle is showing and make sure it close to actual altitude at the vehicle's location.

    If you can get a copy of the sensor readings at different operating conditions On-Demand should have them or get the sensor reading page from Ford's PCED manual. Check the actual timing advanc from the scantool against the recommended reading. Higher than recommended will cause pinging.

    If the engine is running warmer than normal, around 200 deg F this can also cause a problem

    Make sure fuel rail temperature and pressure sensors are reading correctly.

    Hope this helps

    Larrycng

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    • #3
      Re: Underload detonation

      Thanks for the help LarryCNG. I had asked the same questions at "Just Answers.com" where you pay for advice and your response was actually more detailed and useful. One of the Techs at Just Answers in response as to what diagnostic tool/software I should buy to analyze the Crown Vic issues suggested buying a used Ford Scan tool. Seems like a good idea and it also seems as though you are referencing that device in your responses.

      Again thanks for your generous help/sharing of knowledge.

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      • #4
        Re: Underload detonation

        You're welcome.

        The NGS, I think is still available aftermarket and that was the Ford scantool at the time. You can check with www.aeswave.com and ask for Carlos, he can help you if you are interested. If you are doing alot of Ford work, the NGS is the tool

        The other choice, if you have a lap top, would be to contact Autoengineuity ( www. autoengineuity.com ) ask for Bill. Bill has a lot of experience with Ford CV's and could tell you if the Ford software would do what you want. this one cost less.

        Hope this helps

        Larrycng

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        • #5
          Re: Underload detonation

          Originally posted by larrycng View Post
          .. would be to contact Autoengineuity ( www. autoengineuity.com ) ask for Bill.
          Sorry Larry, but the URL that you posted is incorrect. Here is the correct one, minus the extra space and the subtracting an 'e':

          http://www.autoenginuity.com/


          ?Innovation is driven by having access to things.? -- Gleb Budman, CEO of backblaze.com

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          • #6
            Re: Underload detonation

            Thanks!

            Larrycng

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