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  1. #1
    FEP Power Member fgross2006's Avatar
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    Default Choke thermostat issue

    on my 84 LX 5.0 I have an electric choke thermostat. I think its not functioning because after my car reaches operating temp I still have a racing engine at 1000 in drive and 2000 in park.

    I noticed if I move the cam behind the choke thermostat with my fingers I can drop it into low idle. But the choke should be doing this when the car warms up. I thought perhaps it was rusty so i squirted a bit of WD40 on the linkage but again today from a cold start till I got it to correct idle I had to drive a half hour and restart the car twice.

    I checked for voltage and its getting 14.5 v through the choke thermostat wire. Is it possible the choke isnt responding to voltage anymore? Is there a way to test the choke thermo for continuity? The car didnt always behave this way. I'm sure the issue is the choke and or the cam linkage behind the choke.

  2. #2
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    Behind the plastic choke cap is a spring which fits into a forked lever. Sometimes the spring breaks off or is not engaged.
    Fox Body/3rd Gen MCA Gold Card Judge
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    88 Mclaren Mustang Vert 20K miles, 89 Mustang LX Sport Vert,
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  3. #3
    FEP Power Member fgross2006's Avatar
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    Quote Originally Posted by KevinK View Post
    Behind the plastic choke cap is a spring which fits into a forked lever. Sometimes the spring breaks off or is not engaged.
    good possibility. Ill have to pull the cap off and check. I was wondering if I pull the choke stove off and apply 12v from a battery to the positive electrode and ground it out would I see if the spring moves?

  4. #4
    FEP Senior Member BMW Rider's Avatar
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    The choke cap just has a simple heating element to warm the bimetal spring. Check it for continuity. The other area where problems arise is the ground side of the housing. There is a ground tab on the outside of the cap that relies on the retainer ring to complete the ground to the carb itself. Common to see some corrosion on that. Remove the cap and check the element, buff up the ground tab and the retainer ring and clean the mating faces on the carb and see what happens.

  5. #5

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    Also there is a weighted ball molded into the cam. These break off and the cam won't move down all the way to fully come off choke.
    Here is the cam:
    https://www.jegs.com/i/Holley/510/45...iABEgJbJvD_BwE
    85 GT - owned since 87

  6. #6
    FEP Power Member fgross2006's Avatar
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    Quote Originally Posted by BMW Rider View Post
    The choke cap just has a simple heating element to warm the bimetal spring. Check it for continuity. The other area where problems arise is the ground side of the housing. There is a ground tab on the outside of the cap that relies on the retainer ring to complete the ground to the carb itself. Common to see some corrosion on that. Remove the cap and check the element, buff up the ground tab and the retainer ring and clean the mating faces on the carb and see what happens.
    How do i check for continuity? check ohms accross the positive terminal and the ground ? whats should the reading look like?

  7. #7
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    I don’t believe you will find a ball weighted cam on the CFI choke linkage.
    Fox Body/3rd Gen MCA Gold Card Judge
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  8. #8
    FEP Senior Member BMW Rider's Avatar
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    Quote Originally Posted by fgross2006 View Post
    How do i check for continuity? check ohms accross the positive terminal and the ground ? whats should the reading look like?
    Yes, from the power terminal to the ground tab. I don't recall the readings one should expect, but it should not be very high resistance. If the element has failed, you'll have zero continuity much as you would with a burnt out light bulb.

  9. #9

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    I don’t believe you will find a ball weighted cam on the CFI choke linkage.
    Sorry! I missed the in drive part, thinking carb.

    Mike
    85 GT - owned since 87

  10. #10
    FEP Power Member fgross2006's Avatar
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    does anybody know the exact Motorcraft part number for the 5.0 CFI choke thermostat?

  11. #11
    FEP Senior Member Matt J's Avatar
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    I got mine from the local NAPA, so if you can't find it from Motorcraft that should work. I'm sure it was used on lots of different models.

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