Curb idle setting 1985 Motorcraft/Holley 4180C
- Thread starter Woody1965
- Start date
You have many responses to this on another thread, https://stangnet.com/mustang-forums/threads/1985-holly-4180c-high-idle.928104/
You have not checked anything in this thread?
No pics of your linkage?
Two major factors on a carb that effect idle, timing and vacuum.
You have not checked anything in this thread?
No pics of your linkage?
Two major factors on a carb that effect idle, timing and vacuum.
85GTStangGuy
5 Year Member
Reference the first statement in the following post...
stangnet.com
With the a/c off, that screw should adjust your idle speed. With the a/c on, the solenoid should push the idle kicker out a bit, raising the idle speed, offsetting the idle speed that the a/c compressor drags down.
Did you do and/or check everything that was brought up in your other 4180C high idle thread?
Edit - 4-star beat me to it!
Engine - 1985 Holly 4180C high Idle
I have and owen this stock 1985 5.0L 302 Mustang GT all of its 40 years, has about 71,000 miles on it, About 10 years ago it started to have a high idle, ill say when warmed up and choke is off. 1,100 RPMs I have had the carb rebuilt since then but still a high idle, (That is not the...
stangnet.com
With the a/c off, that screw should adjust your idle speed. With the a/c on, the solenoid should push the idle kicker out a bit, raising the idle speed, offsetting the idle speed that the a/c compressor drags down.
Did you do and/or check everything that was brought up in your other 4180C high idle thread?
Edit - 4-star beat me to it!
There are two idle adjustments, one is hot idle-see the adjustment screw on the linkage behind the ball-stud?
The other is the fast-idle on the kick-up attachment.
There maybe an adjustment on the opposite side depending on electric, vacuum or manual choke.
Had to hunt the dark depths of my memory, with help from Googlefu, since I don't have hands on here, not many members around that fuss around with stone-age car parts.
You also don't say if you checked anything suggested in the other thread.
ebay pic, only carb I got now (I thinkYours is purtier than mine General....
There are two idle adjustments, one is hot idle-see the adjustment screw on the linkage behind the ball-stud?
The other is the fast-idle on the kick-up attachment.
There maybe an adjustment on the opposite side depending on electric, vacuum or manual choke.
Had to hunt the dark depths of my memory, with help from Googlefu, since I don't have hands on here, not many members around that fuss around with stone-age car parts.
You also don't say if you checked anything suggested in the other thread.
There are two idle adjustments, one is hot idle-see the adjustment screw on the linkage behind the ball-stud?
The other is the fast-idle on the kick-up attachment.
There maybe an adjustment on the opposite side depending on electric, vacuum or manual choke.
Had to hunt the dark depths of my memory, with help from Googlefu, since I don't have hands on here, not many members around that fuss around with stone-age car parts.
You also don't say if you checked anything suggested in the other thread.
85GTStangGuy
5 Year Member
I agree.... I believe that is a Cali only carb (or maybe the high altitude version) of the 4180. The Mustang 4180C's (std 49-state versions) have the idle adjustment screw on that turned-in tab about an inch above the ball stud. (As shown in the pic in post #5.)
@Woody1965 - Like @limp and I have said multiple times, that screw that pushes against the a/c throttle kicker should adjust your curb idle. Have you tried what @limp said to do in post #5? If the idle won't lower that way, than I'd guess the a/c throttle kicker is not adjusted correctly, or is not functioning properly.
Does the idle speed change any with the throttle linkage disconnected?
Well without the carb in front of me I'm stabbing in the dark.
Look on the side of the choke assembly, loosen the three small screws around the parameter, that will allow that round part to turn clockwise and counter clockwise, one way raises idle, the other lowers it, first adjust the idle with the engine at operating temp, the check idle cold, I know it sounds backwards.
Again hard to diagnose from this far away, based on what I read between the two threads on this issue I still feel it's a vacuum issue.
Look on the side of the choke assembly, loosen the three small screws around the parameter, that will allow that round part to turn clockwise and counter clockwise, one way raises idle, the other lowers it, first adjust the idle with the engine at operating temp, the check idle cold, I know it sounds backwards.
Again hard to diagnose from this far away, based on what I read between the two threads on this issue I still feel it's a vacuum issue.
As the General says, there should be 3 screws that hold the black choke part on..
Personally I would loosen those and twist it so the choke isn't even working to take it out of the search for whats causing this.
There is also a Choke pull off, that applies vacuum to the choke flap when the car starts... Check if its working.. If its losing vacuum and allowing the choke flap to come back on, even a little bit, this could raise your idle....... Pull off the vacuum line to it and attache a hand held vacuum pump and see if it holds vacuum.....
Best way to adjust your choke is to do this in the morning after letting your car sit overnite.. ... DO NOT turn the key on at all... You do not want to heat up your choke coil..
loosen the 3 screws and adjust it so the choke flap just barely opens or starts to open... Tighten the 3 screws and that at least gives you a good base to start from.. Although my experience has been that there is usually no need for more
You have been giving many things to check by people on here... Can you tell us what you have done so far?????
85GTStangGuy
5 Year Member
Two things....
First, unless his carb has been messed with before, the "screws" holding the choke cap to the choke housing are not really screws. They are... but they are the breakaway-head style... so there is nothing there (no slot) to turn them with. They need to have a slot added (via a small cutoff wheel or a carefully used hacksaw blade) in order to be able to remove them. And you need to have the replacement screws that you are going to use in place of the now buggered-up factory screws.
Second... and I can't guarantee this (it's been decades since I've been into a 4180C)... but I seem to recall that the choke cap is keyed to the housing. In other words, there is no rotating the choke cap in relation to the housing. I would really like someone else to either verify this or disprove it... it just sticks in my mind for some reason.
Hey @limp, I see your oe carb has screws for the choke cap. Can you pop them off and see if the cap rotates? And also if it's an original Ford choke cap? I think aftermarket choke caps lack the "key" on the cap (which is what clocks it to the housing in a specific orientation).
Again, I may be confusing this with some other factory carb I messed with...
Thanks everybody for their help.
I have checked for a vacuum leak have not found that
I’ve cleaned out the EGR
What I did notice is that the throttle didn’t go all the way back, seem to stop about 1/32
I added an extra return spring and it seem to help
The gas pedal was touchy
I ended up looking at the linkage bracket and I was able to reposition it about a8 of an inch forward that seemed to push that all the way
I’ll see how this goes. Thanks for everyone’s help.
85GTStangGuy
5 Year Member
Looks sharp. And shiny. The headlight covers, taillight covers and louvers are all period stuff.... pretty neat. Not a fan of the extra decals though... would look cleaner without them, imo. Overall tho, nice ride! 
Yes cap rotates... Looks like Billy Bob did this as there are 2 slotted screws and one philips..
Choke cap says Motorcraft.. See pic
I got to use my new crescent wrench.... Its billet aluminum and its small enough, 8 inches, but the jaws allow for a good sized bolt or fitting..
I bought 2 of these at $14 each, normally $89 each on a close out at Holley... Free shipping too..... In case anyone else is interested .....
Choke cap says Motorcraft.. See pic
I got to use my new crescent wrench.... Its billet aluminum and its small enough, 8 inches, but the jaws allow for a good sized bolt or fitting..
I bought 2 of these at $14 each, normally $89 each on a close out at Holley... Free shipping too..... In case anyone else is interested .....
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