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Thread: Bad Gas Milege, Off Idle Hesitation/Stumble

  1. #11

    Default Bad Gas Milege, Off Idle Hesitation/Stumble

    Yes I have recently made some of the suggested adjustments without a full reset, so I will definitely do that prior to the new tweeks. As well I did mark the allen heads to keep better track of throttle blade adjustment. Well I'll try these things see where it gets me, and repost. Thanks for the input Guys.

  2. #12

    Default Bad Gas Milege, Off Idle Hesitation/Stumble

    I ran across a MSD addendum regarding part throttle hesitation, and mid range sluggishness, when using PWM no regulator. It's a Airtex fuel pressure damper. I found the damper, but can not seem to find the part # MSD32095 adapter, or the #WAS32185 washer, and #HDW31053 O-ring for the adapter. Could I get some information where I could get these items.

  3. #13

    Default Bad Gas Milege, Off Idle Hesitation/Stumble

    Have tried out a few different configurations, cam settings, timing, idle settings, total timing, Etc.

    It's running very well fuel mileage improved, good acceleration, and good idle. Still have hesitation. Waiting for fitting to install fuel pressure damper that should take care of that problem.

    Current settings

    Cam: Mild

    Idle: 750 RPM

    A/F Idle: 14.0

    Cruse: 14.7

    WOT: 12.8

    Initial Timing: 14 Degrees

    Timing in @ 850

    Total Timing 36 Degrees

    Total Rpm 2700 RPM

    Vacuum Adv. 10 Degrees

    Ported Vacuum

    IAC @ 0 in gear

    These setting working very well with my application.

    Thanks to all for input. If the fuel pressure damper takes care of the hesitation the world will be a better place.


  4. #14

    Default Bad Gas Milege, Off Idle Hesitation/Stumble

    I'm concerned that the MAP reading is off. At 500-ft the Key-On, Engine-Off MAP value should be about 29.4"Hg (more or less).

    With the MAP reading a lower pressure than actual, the mixture will be leaner.



    Are any of the other sensor values such as the IAT, fuel pressure or ECT reading odd values also? If so, the small black wire on the power module may have a bad ground.

    If only the MAP value is off, then the MAP sensor needs to be replaced.

  5. #15

    Default Bad Gas Milege, Off Idle Hesitation/Stumble

    My exact elevation is 628 ft. Map still 27.5 key on, 16.1 running

    running ECT 151, IAT 129, Fuel Pressure @ idle 40 PSI. All else seem normal besides MAP.

    How do I go about getting New MAP Sensor?

  6. #16

    Default Bad Gas Milege, Off Idle Hesitation/Stumble

    GSchafer. Im not for or against ported or unported wacc. But Jhon

    Hinckley has wrong in one part in his writing.

    He states ported wacc was used first time in the late 60's due to polution regulations.

    This may be tru to GM but in my Ford shop manual -59 they used ported wacc on all engine.

  7. #17

    Default Bad Gas Milege, Off Idle Hesitation/Stumble

    This is true, in fact they vacuum advance actually used to move the distributor chassis in order to advance or retard the timing and it was always above the throttle plates.

    The vast amount of people that I deal with that have daily driven or at least street driven cars benefit from ported vacuum. Race cars or high lift cam cars, not so much.

  8. #18

    Default Bad Gas Milege, Off Idle Hesitation/Stumble

    fcsallan wrote:
    This is true, in fact they vacuum advance actually used to move the distributor chassis in order to advance or retard the timing and it was always above the throttle plates.

    The vast amount of people that I deal with that have daily driven or at least street driven cars benefit from ported vacuum. Race cars or high lift cam cars, not so much.

    So, what you are saying is that the lean fuel charge while idling requires the exact same amount of timing as the fuel charge that has been enriched by the accelerator pump when you step on the gas at idle rpm? I have a hard time believing that, unless you are idling with a rich mixture.

    Didn't Ford use a thermostatic control valve that forced the distributor to use ported vacuum unless the temp got too high when it would revert to unported vacuum to cool the engine down? I'm just asking, because I just read about it today. i don't know why the older Fords used ported vacuum. I could only guess that they needed extra heat in the combustion chamber to run right?

  9. #19

    Default Bad Gas Milege, Off Idle Hesitation/Stumble

    If u use wacc adv at 10 deg and ported initial at 12 the spark will be there at 12 degres.

    if u use wacc adv at 10 deg and unported initial at 2 the spark will be there at 12 degres

    The same thing diffrent means to get ther I suppose.

    Attached files


  10. #20

    Default Bad Gas Milege, Off Idle Hesitation/Stumble

    MSD Atomic EFI Support wrote:

    I'm concerned that the MAP reading is off. At 500-ft the Key-On, Engine-Off MAP value should be about 29.4"Hg (more or less).

    With the MAP reading a lower pressure than actual, the mixture will be leaner.



    Are any of the other sensor values such as the IAT, fuel pressure or ECT reading odd values also? If so, the small black wire on the power module may have a bad ground.

    If only the MAP value is off, then the MAP sensor needs to be replaced.

    Blazer,

    Any feedback on this?

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