94' Trans Am the car starts runs great till 175-180 degrees and just shuts off. Let it cool for awhile starts back up. Check fuel pressure, thats great, have no spark. Swapped coil, icm assembly off a running car, started then about 180 degrees it died. No DTC's.

 

Can you tell if its does it right when it switches to closed loop? You can disconnect the 02 sensors and see if it still happens. Have you checked fuel pressure as it dies? Have you scanned it for codes or just saying there is no check engine light on? Probably something electrical is breaking down after it gets up to temp. Guessing that heat soak may be causing optical cam position sensor in the Opti to fail after getting hot. Here are a couple threads to read. A search will results in 100's of good ones to read.

https://www.camaroz28.com/forums/lt1...-while-782492/

https://www.camaroz28.com/forums/lt1...egrees-772108/

 

I just went through a similar issue with my 94. When it would reach about operating temp it would start running real bad like it was missing. It seemed alot like ignition issues to me but after alot of hair pulling it turned out to simply need new o2 sensors. ran like new after that