i have a 84TA with the 305, and the electronicaly controled carb....well sometimes in the morning or whenever i let my car sit for a little bit, i have a problem with the idle. the car will start fine, then i will let it warm up for a while. usualy when you here your car at high idle, you hit the gas a little and it will kick the idle down....or atleast thats what my moms 86 caprice does. My car does not. When i tap the gas the idle either stays the same (usualy around 1500-2000) or goes higher. when i first got the car it was kinda worse, it do this more often and even idle around the 2500 mark. Im pretty sure this is not supposed to happen. any one know what can be wrong?? Since i have first had this problem, i have used some choke/carb cleaner. it helped a little, making my car not do it as much, and kicked the idle down more then were it was at, but still...it doesnt seem normal. If anyone has any suggestions,, please post!! i much appreciate it!

Ryan

ps...isnt the idle supposed to be around 500??

 

even in gear, its closer to 650.

I am pretty sure that the choke pulloff is responsible for determining when the motor is warm enough to allow it to come off of fast idle. It is a little vaccum can on the right side of the carb. Make sure it has a vacuum hose going to it and it is actually functioning as the motor warms up... you should see the little connecting arm move.

You might need a new pulloff. Best thing to do is get a chilton manual.. or pull the aircleaner off of your moms and watch it as someone takes it off the fast idle.. you will see the little pulloff function.

Unless vader wants to draw you a diagram

 

The choke pull-off opens the choke butterfly slightly after the engine starts, and should pull the choke idle cam down to the 1st step down when the trottle is tapped. After that, the warming choke thermostat will gradually open the choke butterfly to the full open position after a few minutes, and the choke idle cam will continue down to lower steps as the throttle is at tapped or depressed.

Make sure the choke is getting the proper 12 volts at the thermostat with the ignition on, and that the thermostat is going to full open within a few minutes after starting (meaning the thermostat is in good shape). You may have gummy mechanisms as well, which could be why the spray carb cleaner helped a little bit. Some disassembly of the choke may be necessary to insure it is all clean.

The pull-off should also be checked as stated above to insure it is working properly.

 

Oh, the stock, warmed-up, in-drive idle speed for my car is 500 RPM. The cold idle speed is slightly higher.

 

ill be sure to check these things out, thanks alot! i wish the guys on the "motor swap" board were this helpful!.....how do i check for a bad thermostat?

 

He meant choke t-stat, not t-stat as in the one for your coolant. As he said in his post, After you've verified that the choke wire gets 12V when the car is running, you need to verify that the choke is opening fully within a few minutes. If it doesn't the choke coil (t-stat) is bad.
It's either no power to the choke, bad choke coil, or dirt/etc on the fast idle cam keeping it from smoothly disengaging. If it's the latter, dissasembly/inspection/cleaning is your best recourse.