I've finally got my car running and it runs pretty good once it warms up. My idling problem is only apparent when I start the car up after sitting overnignt or when the engine is cold. I'm getting a code 23 and the Mat sensor is reading -40 deg. F. on a scan tool. I was just wondering if the MAT could be the reason the car dies when it's cold or if I should look at some of the other sensors for the cause of the idling problems? Once the car warms up it idles fine at a stop, though. Oh yeah, the car is an 89 iroc tpi, 355, hot cam, ported vette heads, mod. intake, PR custom chip.

 

That could be a good possibility. Replace the MAT. If that doesn't stop it start checking wiring.
bsa