The car is a 1984 Firebird 305 with a 4bbl rochester carb stock.

The weather here in Michigan just drop from around 60* to 30* degrees and now the damn car idles at 1900 rpm while in park and about 1100 in gear. But during the summer and fall it idle at like 900 in park and 600-700 in gear. Now that it's idling high when i shut it off it chokes for a good 2-3 minutes. Next to the carb there is a circle device that looks like it should have a tube hook to it but it doesn't could this be the problem? if i replace the O2 sensor will this fix the problem? What exactly will cause it to idle this high?? how do i fix it??

:hail:

 

That black round thing on the side of the carb is the choke element. Anytime the choke is on the idle speed will be increased- there's a "high idle cam" in the choke linkage that raises the idle speed. Your high idle speed is being caused by the fact that the choke is not warming up and therefore you're always on the high idle cam.

An 84 SHOULD have a carb with an electrically-heated choke element (one wire goes to the choke element). The fact that you have a "tube" on the side of yours makes me wonder if this isn't an earlier model Qjet that uses a "hot air" style choke element. This type of choke draws air through a series of tubes. It starts at the back of the carb. Line goes down to the exhaust crossover in the intake manifold. I loops around a piece of tubing inside that passage (which you can't see from the outside) where the air is heated and then out through a second tube which connects to the choke element housing. The air is drawn through these tubes by a very small calibrated vacuum leak inside the choke element which connects to manifold vacuum under the carb via a passage internal to the carb.

If you do NOT have an electrically heated choke element on your QJet I suggest you convert over to one- making the stock hot air style tubing fit a non-stock intake or one that wasn't designed for it is very difficult to do.

You can send me an email if you like and I'll walk you through the conversion. Total cost will be about $40, plus an hour of your time to install it.

 

Thankx for the reply. There isn't a tube on the side of it. There is a circular device on the side on the carb that looks like the end of a tube should be plug into it. I believe it is a electronic choke but i'm not sure. On side of the carb near the circle device there is a smaller device on the side of the carb and when the car trying to shut off it seems to be pushing something out of it? I'm grasping straws here. If i can find a diagram of the carb will this be better?

 

If it's an electronic choke it should have a large single wire connector sticking stright out the side of it. Pretty hard to miss. The connector itself sometimes gets snapped off by a careless mechnic (requiring replacing the choke element).

A diagram would be great. Picture's worth a thousand words.

Don't worry about that retracting thing near the choke- that's the vacuum break diaphragm. If it's releasing (extending) when you shut the motor off then it sounds like it's doing it's job.