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  1. #1

    Default Adjusting cruise control

    Narrowing in on my cruise fine tuning. Found that the feared vacuum leak was not the case (holds 25+ pounds of vacuum with no loss) so I suspect the strange behavior (5mph increase in speed when engaged, surge when you hit coast) was VSS related. Had a new gear put on the VSS when I put the 3.73s in the rear and after hooking the vacuum back up again the cruise is behaving much better. Only a tiny increase in speed when you engage cruise, maybe 1 or 2 mph. Is this a sign of the VSS still being wonky, or is this the throttle actuator needing adjustment? I searched old threads but most of those go from "not working" to "working" without fine details like this.
    1984.5 G.T.350 5.0 CFI AOD Convertible (TRX package, loaded)
    Hooker Super Comp Shorty Equal Length Headers
    GT40 heads, Edelbrock 3721, K&N filter in stock dual snorkel,
    Comp cams XE254H, hypereutectic pistons, catted BBK H-pipe, full custom duals.
    3.73 rear. CS5 225/60/15 on 10 holes (street) Federal 595 rs-rr 225/45/15 on 10 holes (race)
    Everything else stock and fully functional.

  2. #2

    Default

    Adjusted the cable to it's perfect spot, and still have the 1mph increase, so I assume it must be the vss. I can live with it's quirky 1mph thing.
    1984.5 G.T.350 5.0 CFI AOD Convertible (TRX package, loaded)
    Hooker Super Comp Shorty Equal Length Headers
    GT40 heads, Edelbrock 3721, K&N filter in stock dual snorkel,
    Comp cams XE254H, hypereutectic pistons, catted BBK H-pipe, full custom duals.
    3.73 rear. CS5 225/60/15 on 10 holes (street) Federal 595 rs-rr 225/45/15 on 10 holes (race)
    Everything else stock and fully functional.

  3. #3
    FEP Super Member xctasy's Avatar
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    Dunedin 9011, New Zealand, South Pacific
    Posts
    2,898

    Default

    Yep, that's its working accuracy right thur.

    The Variable Reluctor sensor is very old technology...it was around in the first Distro-Vac Boss Mustangs and 351C 4V's, and Maverics. Circa Octoner 1969 or so.


    Like all sensors. they can fail to make a clean pickup signal.

    When worn, what a very strange system the Fox VR is.. It's just the 8000 plips per mile, early EECIV compatibale 8 pulse per speedo cable revolution VRS system, with a variable voltage square wave form from 20 mph onwards. It does have some funny features on sub 20 mph voltage polling, technically able to poll back down to 7 mph in some circumstances.

    As you may be aware, certain versions of the EEC III, EEC IV and most EEC V's require an 8000 pulse per mile vehicle speed sensor signal from the PSOM (speedo module), which is just like all other EEC-IV equipped vehicles

    Other later EEC V applications use a 16000 or 40000 pulse per mile VSS signal. The Fox VR VSS sensor can waer, and the signal can be shoddy.



    I'm told that some of the CFI or Speed Density AOD Fox varints in the LSC Lincolns had the potential to use the polling right down to 7 mph, and allow idle speed conditioning.



    I've posted the photos elseware on several other forums,

    (EG
    http://www.fordmods.com/ford-v8-f2/a...c-t107950.html

    http://vb.foureyedpride.com/showthre...t-verses-speed)

    but I pulled the signal out on my 1981 Stang, and found the periodic zero mph to 19.9 mph null readings don't increment, just like some ABS circuits. It has no reliable squarewave below 20 mph to log distance travelled.

    I jacked up my car, and ran the standard Hetz, A/C Voltage and Ohms resistance checks from zero to 62 mph, with my metric speedo registering in KM/H. Note that there is no voltage going up to 32 km/h or 20 mph, but once invoked, the voltage can be recorded right donw to zero, so there is an interesting voltage speed, Hertz resolution

    0 km/h, 0 mph 0 Hz, zero volts AC
    12 km/h, 7.4 mph, but 0.016 volts AC on over run
    See picture
    Image
    20 km/h, 12.4 mph 0 Hz, zero volts AC
    30 km/h, 18.6 mph 0 Hz, zero volts AC, but 0.033 volts AC on overun
    See picture
    Image
    32 km/h, 19.9 mph 0 Hz, 0.00 volts AC
    32.2 km/h, 20.0 mph, 0 Hz, 0.019 volts AC
    40 km/h, 24.9 mph 0.056 volts AC
    50 km/h, 31.1 mph, 0.083 volts AC
    60 km/h, 37.3 mph 102 Hz, 0.109 volts AC
    70 km/h, 43.5 mph, 0.149 volts AC
    80 km/h, 49.7 mph 0.186 volts AC
    88 km/h, 54.7 mph 125 Hz, 0.223 volts AC
    See picture
    Image
    100 km/h 62.1 mph, 0.273 volts AC
    See picture
    Image


    The square wave form kicks in after 19.9 mph on the upward rise, with zero Hertz cycles per second on my Cat IV multimetervoltage and the voltage increasing steadily from 20 mph on upwards.

  4. #4

    Default

    so you are telling me I should jiggle the wires.
    1984.5 G.T.350 5.0 CFI AOD Convertible (TRX package, loaded)
    Hooker Super Comp Shorty Equal Length Headers
    GT40 heads, Edelbrock 3721, K&N filter in stock dual snorkel,
    Comp cams XE254H, hypereutectic pistons, catted BBK H-pipe, full custom duals.
    3.73 rear. CS5 225/60/15 on 10 holes (street) Federal 595 rs-rr 225/45/15 on 10 holes (race)
    Everything else stock and fully functional.

  5. #5

    Default

    Quote Originally Posted by emerygt350 View Post
    so you are telling me I should jiggle the wires.
    I lolled at that.
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI T-5 (Mustang LWB)
    '17 Ford Transit Connect Titanium LWB
    '14 Ford Fusion SE Manual

  6. #6

    Default

    Quote Originally Posted by emerygt350 View Post
    so you are telling me I should jiggle the wires.
    Or ship your car to NZ for troubleshooting.
    1985 GT, Sunroof, 5 Lug, Rear Discs, 01 Graphite Bullets, 88 forged piston shortblock, 2.02/1.60 Alum heads, Weiand Stealth, Holley C950 TBI, BBK Long tubes

  7. #7
    FEP Super Member xctasy's Avatar
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    Default

    lol.


    Its okay...wiring "gettin giggy wit it" is good. Advice, well it's just a repeat prescription.


  8. #8

    Default

    Sadly, it snowed today... So the mustang season is over. I will have to look at wave forms or jiggle wires next spring. So sad.
    1984.5 G.T.350 5.0 CFI AOD Convertible (TRX package, loaded)
    Hooker Super Comp Shorty Equal Length Headers
    GT40 heads, Edelbrock 3721, K&N filter in stock dual snorkel,
    Comp cams XE254H, hypereutectic pistons, catted BBK H-pipe, full custom duals.
    3.73 rear. CS5 225/60/15 on 10 holes (street) Federal 595 rs-rr 225/45/15 on 10 holes (race)
    Everything else stock and fully functional.

  9. #9
    FEP Power Member 85stanggt's Avatar
    Join Date
    Nov 2005
    Location
    Tampa, FL
    Posts
    2,199

    Default

    My car has always had that slight surge when engaging cruise and coasting. I feel like it is just the system taking control of the throttle, and then metering the speed once all readings level out. My BMW does the same thing...

    Are you saying it should not do that?
    1985 Mustang GT Convertible
    Stock and original @ 213k, except for dynomax ultraflos.

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