81 Choke / Fast Idle operation
Thread Starter
Le Mans Master
Joined: Feb 2000
Posts: 7,032
Likes: 2
From: Newburgh NY
81 Choke / Fast Idle operation
My friends 81 has a problem with it idling too fast. If I pull the choke butterly back when I pump the gas, it will idle fine. If you just punch it, the choke will stay partially open and it idles way too fast.
This is a partially ECM controlled car and I don't know if that has anything to do with it. The electric connection to the choke housing is hot (put a tester on it). If I reach behind the choke and push down on the lever it will stay open, but it doesn't lock in place on it's own.
Is this an adjustment, or an electrically/mech problem of some type. Anyone have a similar situation?
Thanks
This is a partially ECM controlled car and I don't know if that has anything to do with it. The electric connection to the choke housing is hot (put a tester on it). If I reach behind the choke and push down on the lever it will stay open, but it doesn't lock in place on it's own.
Is this an adjustment, or an electrically/mech problem of some type. Anyone have a similar situation?
Thanks
Safety Car
Joined: Mar 2000
Posts: 4,078
Likes: 27
From: Northeast South Dakota
Re: 81 Choke / Fast Idle operation (78Vette-SA)
If the choke is not opening all the way and that is causing the fast idle it is just an adjustment. The ECM doesn't have anything to do with choke function. It does know if the engine is 150 deg. F. or not though. Open or closed loop is dependent on the engine temp being above or below 150 deg. If the choke is partially open and when you open it up the idle goes right down it is an adjustment just like any other q-jet that is the problem. probably the electric choke pulloff. I'll check this topic again after work tonight. Later.
-Justin
-Justin
Racer
Joined: Oct 2000
Posts: 321
Likes: 0
From: Aptos, CA.
Re: 81 Choke / Fast Idle operation (Dalannex)
I'm with Dalannex on this. It sounds like the pull-off isn't working. To check, have someone start the car while you watch the unit (front r/s of carb above fuel inlet) and watch the arm while the person starts the car. You should see it move in toward the pull-off unit. If it doesn't, that's your problem (provided you have vacuum to the unit, which I'm sure you do). If it does work, the choke needs adjusting and/or choke cover (coil heater) needs replacing.
The pull-off requires constant vacuum and you can test it with a vacuum pump or just a hose connected to it and then drawing vacuum with your mouth. (Time for remarks here) :)
The pull-off requires constant vacuum and you can test it with a vacuum pump or just a hose connected to it and then drawing vacuum with your mouth. (Time for remarks here) :)
Thread Starter
Le Mans Master
Joined: Feb 2000
Posts: 7,032
Likes: 2
From: Newburgh NY
Re: 81 Choke / Fast Idle operation (weendoggy)
Pull off was working. I also let the engine warm up good, to about 180+.
Sounds like just an adjustment then. I assume to adjust it just loosen the 3 small allen heads around the unit and turn the housing. Probably to the right to ease it up (less choke) and left to make it more choke?
Thanks guys
Sounds like just an adjustment then. I assume to adjust it just loosen the 3 small allen heads around the unit and turn the housing. Probably to the right to ease it up (less choke) and left to make it more choke?
Thanks guys
Racer
Joined: Oct 2000
Posts: 321
Likes: 0
From: Aptos, CA.
Re: 81 Choke / Fast Idle operation (78Vette-SA)
To adjust the choke properly on the '81 carb. you need to use a degree bubble tool, but, you don't really need it. With the engine cold, set the choke, then use a vacuum pump (plugged into the pull off) and apply vacuum. This will open the choke a little. Use a 3/16" drill bit to fit between the choke plate and the air horn itself. Don't drop the bit. ;)
With the vacuum holding the pull off and you applying a little pressure to open the choke, adjust the choke coil by turning the screw on the pull off mechanism to set the choke to allow the drill bit to just fit between the choke plate and air horn.
The choke coil shouldn't be adjustable as it is "pin" fitted to the carb. Also, make sure the choke coil is opening and not closing under heat. Someone may have put the wrong coil in the body. They make them either way.
With the vacuum holding the pull off and you applying a little pressure to open the choke, adjust the choke coil by turning the screw on the pull off mechanism to set the choke to allow the drill bit to just fit between the choke plate and air horn.
The choke coil shouldn't be adjustable as it is "pin" fitted to the carb. Also, make sure the choke coil is opening and not closing under heat. Someone may have put the wrong coil in the body. They make them either way.
Safety Car
Joined: Mar 2000
Posts: 4,078
Likes: 27
From: Northeast South Dakota
Re: 81 Choke / Fast Idle operation (78Vette-SA)
Yeah, try loosening the three screws where the choke heater is (when the engine is cold) and turn the choke heater until the choke flapper just opens, then turn it back the other way until it just closes. Then tighten your three screws back up and see how that works.
I'll stay tuned. :)
-Justin
I'll stay tuned. :)
-Justin
Safety Car
Joined: Jul 2001
Posts: 3,921
Likes: 2
From: York PA
Re: 81 Choke / Fast Idle operation (78Vette-SA)
The electric connection to the choke housing is hot (put a tester on it).
[Modified by stickboy, 1:32 AM 3/30/2004]
