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  • Misfire and no check engine light?

    My 06 Freestar with 127,000 miles has been running like a champ. It's been dead nuts reliable, never missing a beat. The only issues I've ever had was a bad wiper switch and brake light switch that would turn the brake lights on when it got cold over night.

    The other night coming back from PA, I felt a little hiccup from the engine and thought it was odd. Yesterday I noticed it feels like it's misfiring at times while accelerating and cruising. The check engine light never came on and still is off which I'm thinking might be an injector that's clogged or dirty. I would thing if it was a spark issue, the raw fuel in the exhaust would trip the O2 sensor. I was also thinking maybe the EGR valve.

    I think first I will replace the 127,000 spark plugs as a good start
    Tom
    Overdrive is overrated



  • #2

    Re: Misfire and no check engine light?

    Sounds like a good place to start, both of those came to mind for me as well.......Also when was the last time you changed your fuel filter..........

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    • #3

      Re: Misfire and no check engine light?

      Any mis-fire in the cylinder will create a lean condition on the O2 sensor, rather the cause was lack of spark or plugged up injector.

      At 127,000 miles, I'd start with plugs and go from there. Maybe EGR cleaning too.
      Escaped on a technicality.

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      • #4

        Re: Misfire and no check engine light?

        Thanks guys! I'm suspecting the EGR as the car was running great on one tank, then the next tank it started. I know you're thinking bad gas...could be but I gas up at the same place that has high traffic. It could be a bad tank of gas but it's low on my list but not forgotten.

        Feels like the early 70's cars when they first came out with EGR and would surge at part throttle.
        Tom
        Overdrive is overrated


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        • #5

          Re: Misfire and no check engine light?

          EGR is more for when you are coasting though. most times its plugged up all the way back thru the intake manifold. We cracked a plenum on a chevy 3.1, got another one off ebay and used three cans of carb cleaner before we got it clean.

          Check your vacuum connections on the MAP sensor, that controls your fuel pressure and might make a sticky injector really start spitting. These damn engines compensate enough where it wont throw a code for a few weeks.

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