Car info: 1984 L69 305 H.O., Quadrajet carb

I recently fixed my code 15 problem (bad connection to coolant temperature sensor) for good, but unfortunately this made another problem show up.

I got the carb rebuilt last summer and it was set to fast idle at 1200 RPM and regular idle at 500 RPM. It had been working fine with the only problem being that it was always in open loop. Now that the coolant temperature sensor is working correctly, the car now goes into closed loop mode (although I don't think the Torque converter locks up, but thats for another thread...)

If I turn on the car in the morning after being off all night, the car will start at the high idle speed (1200 RPM). When I blip the throttle, it will drop down to normal idle speed. The problem that it has now is that when I turn off the car (for example, when I go to class for a few hours) and then back on, it will idle at an extremely low speed around 300 RPM. Once it goes into closed loop, the idle will go back to normal.

How can I make it idle at the correct speed when in open loop and the motor is warm?

 

Why dont you just turn up the idle screw ?

 

That's not a good idea. The idle should be set where it belongs, not to some level to crutch a specific condition, which will make it wrong for other conditions.

Are you giving it a little throttle before you start it after class? You don't need to floor it, but give it a little gas before turning the starter over so the choke high idle can come on.

Also, have you adjusted the idle air bleed? Open loop is pretty dependant upon it being set correctly.

 

Yes, I usually press the gas pedal once or twice before starting it.

Nope, I havent touched the Idle air bleed after it was rebuilt. Could it be that the person who rebuilt it had to adjust it to a setting not normally used in order to make up for it being in open loop all the time to get it to run well? If so, maybe I need to adjust it, but I dont know how.

 

You can pre-set it on the bench, but the final has to be with the car running.

You need a throw-back from the old days of points ignition, a dwell meter. With the meter on the 6 cylinder setting, connected with the positive lead to the green connector that doesn't go anywhere over by the AC housing, and negative lead to ground, make small adjustments to the IAB until it settles in a 30 degrees.

It may not make much difference, but it should be properly set, anyway.

Other possibilities: Your fast idle cam isn't going on all the way. The choke pull-off is adjusted such that it pulls off too much. The choke thermostat isn't closing the choke all the way.