Holley fast idle driving me nuts! - Team Camaro Tech
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Old Dec 5th, 16, 10:11 PM Thread Starter
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Alex
 
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Holley fast idle driving me nuts!

I have a new AED 750 HO (Holley 4150) with electric choke. This is on a 461 Pontiac engine so it's an air gap Torker II intake, has a divorced water crossover, a blocked heat passage crossover, and I have a 1/2" wooden spacer from AED under the carb. Trust me, I need all that in the summers here, I even have to heat wrap my fuel lines lol.

THE PROBLEM:

I can push my gas pedal just a tiny bit and the choke flap closes. I hit the key and it she fires right up, BUT she will BARELY idle and wants to die. I have to ever so slightly add a TINY bit of gas pedal so she doesn't stall. After about a minute then the fast idle finally kicks in and the idle will increase so I can let off the pedal totally. Then once I see 100f engine temp another minute or 2 later I can romp the pedal, disengage fast idle, and drive off. Temperature is about 50f now when starting.

WHAT I'VE TRIED:
I have checked the choke pull off and it's working fine. Second the engine fires, it opens a bit. Also I know the fast idle is set when the engine is hot, which I have done per Holley to about 1,100-1,2000, I don't need it higher than that.

I called AED and they suggested I richen up 4 corner idle mixture screws 1/8 of a turn each. I did, no improvement and I had a stronger exhaust smell at idle so I went back to where I had them at max vacuum.

I seem to have the timing of the choke plate where it likes it (1-2 notches to the rich side), soon as she idles smooth at 100f I can drive off and she runs great, no stumbles, and doesn't want to die. I have noticed however that after being parked for not a long time, the stupid thing seems to close again too much. I was told buying this should fix that problem: https://www.holley.com/products/fuel...s/parts/45-267 - Where is the best place to attach that thing on the engine?

I have been adjusting the damn fast idle screw every single day for a week and I'm loosing my mind. No amount of adjustment seems to make it so she will idle on her own at cold start for the first minute until the idle finally starts to go up. I've also noticed that if adjusted too much, it will give me a false high idle when hot, so I back the fast idle back off again.

I know the damn fast idle is engaging OK and the screw is touching the plastic cam correctly because like I said, after about 45 seconds to 1 minute, she starts going up in RPM to the fast idle settings.

So, WTF lol. What am I missing here guys? Am I just destined to have a not perfect cold start because of my engine combo maybe? I am seeing about 10.5-11 inches of vacuum at hot idle. The Torker II also runs purrs at idle when warm, you would swear it's a dual plane. Maybe tho it just hates cold winter starts?

Thanks!!!! Alex


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Old Dec 6th, 16, 07:32 AM
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Re: Holley fast idle driving me nuts!

Two options install a manual choke in place of the electric one and use a stiff wire (I used a section of wire coat hanger) to hold the choke open at all times. Second option remove the choke mechanism, and the electric control, and taw off and grind smooth the choke horn. The first option gives you a functional choke for when it snows ion southern California, the second option provides for a freer breathing carb.

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Old Dec 6th, 16, 09:53 AM Thread Starter
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Alex
 
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Re: Holley fast idle driving me nuts!

Haha, nice lol.

So you're saying I've done all that can reasonably been done, and it just is what it is?


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1969 Pontiac Firebird
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Old Dec 6th, 16, 10:05 AM
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Re: Holley fast idle driving me nuts!

Assuming you have the adjustment on the electric choke turned the correct way so that it isn't activating too soon and staying on too long then yes. The black portion of the electric choke turns to rotate the bimetal strip inside the same way the bimetal strip in your homes thermostat works to set your homes heater temperature (or in Florida the A/C temperature; because as I write this it is currently 86 degrees outside, and the humidity is at a very muggy 96% due to light drizzle).

I don't run a choke on any of my Holley carburetors as I use a Dominator on most of my engines, but on my last 406 build I ran a HP series 4150 carb that like the Dominator doesn't even have a choke horn. On older carbs I converted over to a manual choke or removed everything and ran a plastic sub stack to smooth the air flow.

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Old Dec 6th, 16, 10:42 AM
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Re: Holley fast idle driving me nuts!

0. Ensure when choke is set on a cold morning, the fast idle cam is lifted into place.
1. The next cold morning, loosen, but keep snug the cover clamps
2. Step on throttle to 3/4 pedal as this sets choke closed and engaged fast idle
3. Start engine and rotate further the cap in direction needed to smooth out its idle, you'll hear it.
4. Tighten cover screws, and yes, it may be past the norm 1-2 marks and this is okay - it runs.

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Old Dec 6th, 16, 12:15 PM
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Re: Holley fast idle driving me nuts!

If the above fails after you have sufficient flap opening, you may need to adjust the fast idle set screw (that may not be seen unless you take an eyeball out and set under the linkage) which can only be done if you use a long flex extension with a 1/4" socket to back out the screw on the red fast idle cam.

Its not a forgiving process for those that have never done this before.

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Old Dec 6th, 16, 01:17 PM Thread Starter
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Re: Holley fast idle driving me nuts!

Everett,

The choke cap you are referring to is adjustable for the purpose of only controlling the speed at which the choke plate opens after startup once 12 volts hits the bimetal spring inside to start heating it. The choke pull off is what directly controls the amount the choke plate "pops" opens upon initial startup. Holley and AED have told me that on this latest generation of choke, this pull off should NOT be adjusted as it is preset with a specific pre-load.

zdld, as I mentioned in my first post, adjustment of the fast idle screw is having no affect for me on initial startup. Also on my carb, I can see it just fine and can use a small wrench to adjust it without any heroics. The fast idle screw is supposed to be set per Holley's procedure when the engine is at full temp, by manually setting the cam an starting the engine, then adjusting. Which I have done. My fast idle speed is set.

My problem is that from the time the engine starts, until the fast idle seems to kick in, is about 45 secs to a minute, during which time my engine idles so low that it will die if I don't add the ever so slightest amount of throttle as to keep it running but NOT to kick the linkage off the fast idle cam.

I'm pretty sure it's a matter of adjusting the pull off, to get the gap set right for how MY engine wants this gap upon initial cold start. But Holley says the new version I have should not be adjusted. In fact they say it cannot be, they did say it *could* be modified but that there is no "adjustment".

So that's where I'm at. Until someone can tell me how to correctly "modify" my newer style Holley choke pull off, like what to bend, how much to bend it, how to ensure I maintain the proper pre-load, etc. I think I'll be up a creek


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Old Dec 6th, 16, 02:47 PM
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Re: Holley fast idle driving me nuts!

I agree that it sounds like the choke pull off needs adjusted. You should be able to verify if that's the problem without modifying anything. The next time you start your car when it's cold, put your hand over the air horn above the choke and restrict the amount of air entering the engine. If the idle improves, that tells you the pull off is opening the choke too far.

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Old Dec 6th, 16, 03:41 PM Thread Starter
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Re: Holley fast idle driving me nuts!

Absolutely, or not far enough, whichever the case may be. It will be a few days though until I can get a friend over to have in the car to start her up for me to do that so I can be under the hood. In the meantime I figured I would post and get some opinions, see if anyone else has ever had a similar problem and how they solved it.

I've also head that I can remove the carb, and under the base plate there is a screw for the secondaries. That I can use this screw to adjust the secondary base blades open just a tiny bit for additional air. I've never personally done that before and I was hoping someone would comment on that as maybe an option as well since Holley says to leave the pull off alone/that it's non-user adjustable.


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Old Dec 6th, 16, 04:35 PM
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Re: Holley fast idle driving me nuts!

I'd say no choke would be needed in Bakersfield anyway.

I ran a car with a Holley and single plane manifold for years in Colorado without one. I'm talking temps of -23*

Hold your foot on the gas pedal for a minute or 2 when cold started to keep it running until it idles on it's own.

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Old Dec 6th, 16, 05:38 PM Thread Starter
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Alex
 
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Re: Holley fast idle driving me nuts!

Haha, very true, and we've all had plenty of cars without chokes before I'm sure. I know I have.

I'm getting older now though and it is nice to just hit the pedal, hit the key, and not have to feather the pedal until it's smooth enough to drive off. I'd rather be doing other things; putting on my seat belt, maybe setting the radio, checking my phone, watching the gauges, maybe talking to my kids, etc.

It's just a nice thing to have, let's leave it at that lol. It is *needed*, of course not.
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Old Dec 6th, 16, 05:59 PM
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Re: Holley fast idle driving me nuts!

There is no adjustment for the choke pull-off.
Remove the cap and you will see the piston on right hand side.
This piston has manifold vacuum on it - hence the reason you had to remove the lead slug before mounting and cork gasket installed between choke housing and carb body - otherwise a leak will happen.
The vacuum pulls the piston against the bimetal spring tension.
One floors the pedal and choke is snapped shut.
Engine starts and as vacuum builds via rpms, this vacuum pulls on the piston and choke plate opens.
Loosen clamps and rotate cap for smooth engine operation.
Fast idle is set at operating temp and cam manually set in place, use finger, and close throttle. Turn for 1400-1600 rpm.
Secondary plate screw you mention does adjust plate opening for bypass.
The easiest tip is unscrew the setscrew and install from the top so it may be adjusted from the top alleviating removal of carb.
Once screw is set and of needs adjustment, use feeler gauge to set opening for best condition and once all adjustments are made, set height of screw using calipers from measuring feeler gauge and exisiting height.
This adjustment is usually for long duration camshafts, not for stock camshafts.

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Old Dec 6th, 16, 07:30 PM
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Re: Holley fast idle driving me nuts!

Quote:
Originally Posted by anguilla1980 View Post
Haha, very true, and we've all had plenty of cars without chokes before I'm sure. I know I have.

I'm getting older now though and it is nice to just hit the pedal, hit the key, and not have to feather the pedal until it's smooth enough to drive off. I'd rather be doing other things; putting on my seat belt, maybe setting the radio, checking my phone, watching the gauges, maybe talking to my kids, etc.

It's just a nice thing to have, let's leave it at that lol. It is *needed*, of course not.
My apologies if I came across as a jerk.

It's what I do best.

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Old Dec 7th, 16, 10:49 AM
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Re: Holley fast idle driving me nuts!

Press the gas pedal ALL THE WAY to the floor to set the choke. Set low speed jets to 1 1/2 to 2 turns out.
If need be, adjust fast idle screw to 1300/1500 rpm. Good luck.

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Old Dec 8th, 16, 07:41 AM
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Re: Holley fast idle driving me nuts!

All good info suggested so far but I'll add what I can and hopefully it will help you out. First off your high idle doesn't kick in a minute or so after starting, it's mechanical and kicks in the instant you open the throttle to set the choke when it's cold. I believe what you describe as the high idle kicking in about one minute into a cold start situation is the engine responding favorably to the air fuel mixture with the choke butterfly at the position it is at when the rpm's start picking up. If the mixture is either too rich, or too lean, the fast idle setting cannot correct the rpm's of the engine on it's own. The only way to correct that is with the choke housing setting (tension on the choke butterfly) or the choke pull-off which is not adjustable without modification to the carburetor.

With this in mind and in my experience Everett's approach will get you the best results unless you decide to try to modify the factory preset choke pull-off operation. In a sense you are tuning the choke pull-off to some degree using the adjust-ability of the thermostatic choke housing. If the thermostatic choke housing is set a bit too rich (more tension) the choke pull-off will not be able to fight the extra tension and you'll have too rich of a mixture and the engine rpm's will be lower than ideal. If the thermostatic choke housing is set a bit too lean (less tension) the choke may not richen up the air fuel mixture enough to keep the engine from going lean and stalling. With this in mind, you mentioned that you've already verified when choke is set on a cold morning, the fast idle cam is lifted into place. So as Everett suggested;

1. The next cold morning, loosen, but keep snug the cover clamps (enough that you can rotate the thermostatic housing by hand, but not so loose that the housing won't hold it's position).

2. Step on throttle once (I like to go all the way to the floor) to set the choke closed and engaged fast idle cam.

3. Start engine and immediately (you need to get this done before the thermostatic choke housing reacts to the heating of the bi-metallic spring) rotate the thermostatic choke housing cap in both directions to determine which direction is needed to smooth out the idle (it might be useful to temporarily unplug/disconnect the power feed to the thermostatic choke housing so you have time to find the sweet spot before the bi-metallic spring starts easing of the choke butterfly tension).

4. Once the engine responds favorably to the new thermostatic choke housing position, tighten the cover screws and reconnect the power feed to the thermostatic choke housing if you disconnected it so it can due it's thing. Don't even worry about where the marks on the thermostatic choke housing end up, all that matters is finding that sweet spot where the engine runs at the higher rpm's of the fast idle cam position.

It may take a few tries but you should be able to get it adjusted better than your description of how it is acting now.

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