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Discussion Starter #1
My bronco will only start and run with the choke completely open (it is an electric choke) and idk why but it started to do that one morning after sitting all night and it was 30 something degrees outside. The spark plugs look normal. Also I have a vacuum leak somewhere behind the dash that I can’t find and when I turn the ac, defrost, or mix on the engine idles very high.
 

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You can eliminate the dash vacuum leak by finding the vacuum supply line in the engine bay. Look near the vacuum reservoir, probably on the passenger side.
I don’t have anything for you on the choke issue. Seems weird that it’ll only run wide open, especially with your vacuum leak. What carb do you have?
 

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Discussion Starter #3
You can eliminate the dash vacuum leak by finding the vacuum supply line in the engine bay. Look near the vacuum reservoir, probably on the passenger side.
I don’t have anything for you on the choke issue. Seems weird that it’ll only run wide open, especially with your vacuum leak. What carb do you have?
The carb is a remanufactured 4180 and I disconnected the vacuum supply line going into the dash but I could still here the leak coming from behind the driver side dash.
 

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Yo ethanwilliams125,
As packagerjr advised.
Suggest capping HVAC black plastic Vacuum tank on passenger side wheelwell.

152253

152254
 

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Yo,
Vacuum Tank (plastic ball type) pic in an 85 (80-86); passenger side wheel well.
152257
 

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Yo Evan,
Could it b coming from Vacuum Tee on engine firewall?
Pics by Chris B
152260

152261
 

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1986 Ford Bronco, 351w with edelbrock aluminum top end and holly 600.
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Did you hear the vac leak before the choke issue or did it all happen at the same time.

You said it has a carb right?

Are you saying it will only run with the choke closed (not allowing air in) or open?


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Cap all vacuum lines as a first step. My 80 used a vacuum-driven cruise control mechanism under the steering wheel. Maybe your brake booster diaphragm is broken. Eliminate the vacuum leaks before fooling with the carb or you’ll be chasing your tail.
 
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