Problem W/ 93 Es300

[jcf]

I am struggling to figure out why my ES300 is shutting off. Here's the background:

About 3 months ago it overheated on the highway and shut down. I had it towed home and proceeded to check compression and found that it was really out of whack. I pulled the cylinder heads and what I found wasn't pretty. To make a long story short I had the cylinders bored out and new oversize pistons, rings etc installed, valve job, etc at a machine shop. I then installed the engine in the car and now I can start it in cold and it seems to come up fine in high idle. Over the course of 3-4 mins it gradually drops to a normal idle speed (750 rpm). However the moment it begins to reach normal operating temp it begins to drop in rpms to around 500 rpm and then shuts off. Once this happens I can't get it started again. When it cools down I can start it again and it follows the process described above.

Does anyone have any suggestions on how to troubleshoot? I gone thru most troubleshooting steps in the factory manual but no clear culprit found yet.

Thanks,

JCF