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  1. #1

    Default bad power valve, or bad gas?

    I thought I had my stumble/carb issue fixed by replacing my malfunctioning alternator and changing the needle and seat on the primary side of my 4180. Everything was good for a few days. Then I started having a similar bog/stumble at light load, usually under 2k rpm as I was tipping into the throttle. It always seemed to go away right as the secondaries kicked in. So after discussing it with a few coworkers today we came to the assumption the power valve was likely toast. So I bought a regular single stage 4.5 hg one (the only one they had in stock that would fit my carb) at advance and figured I would try it this weekend. While at lunch I filled the car up too, at the same place I almost always get gas, and have for the last few tanks. Well the car ran crappy for about 5 miles leaving work, then all of a sudden it's running perfect again? Ran great all the way home, about another 40 miles. It's gone on and off like this a few times. Can a power valve be intermittent?

  2. #2
    FEP Senior Member
    Join Date
    Nov 2004
    Location
    kennewick, wa
    Posts
    800

    Default

    i think a power valve is either bad or good, not intermittent
    84 GT, 357W, Alum Radiator, 2.02/1.60 Windsor Sr.'s, 600 DP, RPM Air-Gap, CC 270H, 1.6 RR, Streetdampr, T-5, K-C Clutch, Short Throw Shifter, Triple Pickup Quadrant, Firewall Adjuster, BBK shorty's, 8.8, 3.73's, O/R H-Pipe, DynoMax Cat-back, Alum Driveshaft. AFR Monitor, and a couple Auto Meters

  3. #3
    FEP Super Member
    Join Date
    May 2003
    Location
    Roseburg Oregon
    Posts
    3,308

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    Ditto ^^^
    clowns to the left of me , Jokers to the right

  4. #4
    FEP Super Member cb84capri's Avatar
    Join Date
    Jan 2003
    Location
    lansing, mi
    Posts
    4,667

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    how is your fuel filter? is it a busy gas station? is it low quality gas? additives are in the gas this time of year for winter as well.
    Last edited by cb84capri; 11-03-2007 at 12:45 AM.

  5. #5

    Default

    It's a very busy Irving station in Portsmouth NH. I had been filling up close to home up north all summer, because we didn't have the ethanol blended gas up here yet. I noticed in the same exact driving I got 1.5-2mpg better gas mileage on the non-ethanol gas in the mustang. Well, we have the same stuff up here now, and gas is slightly cheaper on the seacoast where I work, so I just started putting gas in the mustang down there a few weeks ago. I've used it in my tacoma during the same period with no issues.

  6. #6

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    So I took the car for a drive saturday, and it ran great. This morning about 1/2 way to work it started it's random sputtering at light load under 2200-2500 rpm with constant throttle again. It's not stumbling when I get on it like it was last week, but it's annoying the crap out of me. I think it's time to put it in the garage, and leave it there till spring. I just cleaned it, changed the oil, and it'll have about 1/3 tank of gas when I get home. Maybe santa (or my wife) will put a 570 street avenger under the tree for me and I can actually not open my hood every other time I drive the car.

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