78Vette-SA

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

Dalannex

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

weendoggy

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) :)

78Vette-SA

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

weendoggy

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.

Dalannex

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

stickboy

This could also be the choke heater relay is bad. Does the choke light at the bottom of the tach stay on? (it should be on when you first start the car and go out when the choke opens the whole way.) The choke gets it's power from 2 circuits, one is the choke light, which does not provide enough current to open the choke. The other is through the choke heater relay (located between the shifter and ash tray) which provide the main power for the choke. You can test the choke by connecting a wire from the main power lug of the alternator, it should open within a few minutes. I had a bad relay and my choke would only open about half way and the choke light would stay on. The '81 service manual has a great diagram of how the choke is wired


[Modified by stickboy, 1:32 AM 3/30/2004]