i have a 305 tbi when i start it up in the morning it idles fine. but when it starts to warm up the idle raises and falls till it eventually stalls.

could this be caused by a vacum leak?

 

i have the same problem

 

any ideas? anyone

 

The ECM does a few things different once the coolant comes up to temp.
As the time-out fueling decays away, the AFR will go leaner. If you have a vacuum leak, it will cause the most problems once the engine goes lean.

Once at a certain temp the ECM will try to switch into closed-loop operation using feedback from the O2 sensor. If the sensor is bad, or you have an exhaust leak near the sensor, you will notice problems with idle.

Also, at a certain temperature a couple of other functions are triggered that use vacuum lines for actuation. One of them is the EGR system. If a system is malfunctioning or there is an open or broken vacuum line, or otherwise a vacuum leak, then it will cause idle problems at this time.

There are many other possible causes, but these are good places to start.
Datalogging is also a great place to start. As you do your testing you might want to post further questions in the TBI section or the DIYPROM section.

 

How clean is the IAC?

 

check t-body mounting gasket very closely for vacuum leaks