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Engine 85 GT Excessive Idle

  • Thread starter Thread starter lutzkecj
  • Start date Start date Friday at 1:58 PM
L

lutzkecj

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Sep 18, 2026
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WI
Friday at 1:58 PM
#1
  • Friday at 1:58 PM
  • #1
I have been working on an 85 GT that is all stock. It has been sitting for a quite a few years. I thought I was having some issues with the stock Holley carb, even after having it rebuilt, where fuel would be pouring out of the carb bowl vents, as well as a very rough/no idle. The only way it would stay running is if I kept my foot on the throttle hovering in that 1200 RPM range. I decided to just replace the carb and went with a Holley 4160. Got it all installed and got the car running. But now it won't go below 2700 RPMs. I tried adjusting the curb idle speed and it still wouldn't budge. I did not mess with the idle mixture at all.

Has anyone else ran into this issue before?

Could this be a fuel pump issue not a carb issue? Or what else could this be? The shop I had work on the car mentioned they cleaned up some vacuum lines so it shouldn't be that.
 

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor
Admin Dude
Jan 4, 1985
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Box behind Walmart
Friday at 2:08 PM
#2
  • Friday at 2:08 PM
  • #2
It sounds like you have a vacuum leak.
 
Reactions: DadLife0724

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
28,030
10,656
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polk county florida
Friday at 7:31 PM
#3
  • Friday at 7:31 PM
  • #3
Some questions,
What fuel pump?
Where's the timing?
Vacuum advance distributor? And is it hooked to port or manifold vacuum?
N/A or power adder?
 
Reactions: AeroCoupe

Blackhawkxx

Mustang Master
Mar 3, 2023
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Saturday at 4:49 AM
#4
  • Saturday at 4:49 AM
  • #4
Are you sure your linkage isn't the problem with the super high idle? Disconnect it and start the car to see.
 
Reactions: AeroCoupe

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor
Admin Dude
Jan 4, 1985
43,353
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Box behind Walmart
Saturday at 10:51 PM
#5
  • Saturday at 10:51 PM
  • #5
lutzkecj said:
The shop I had work on the car mentioned they cleaned up some vacuum lines so it shouldn't be that.
Click to expand...

The fact that these were touched heightens my suspicions.
 
Reactions: General karthief, 86HO5.0 and DadLife0724
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86HO5.0

Active Member
Apr 18, 2023
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Raleigh, NC
Monday at 4:37 AM
#6
  • Monday at 4:37 AM
  • #6
Noobz347 said:
The fact that these were touched heightens my suspicions.
Click to expand...
100%

Always double check what someone else just 'touched'. Too many mechanics nowadays don't know their ass from the Eiffel Tower.
 
Reactions: General karthief and DadLife0724
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