1994 K1500 Suburban Stalling

[sa960]

I'm new here. I have a K1500 1994 suburban about 200 K miles. Idle has been running a little rough for about 12 months . Recently began stalling when at a light or stop/go traffic, the engine usually hiccups a few times and then it stalls out, always stalls when not on the accelerator. It runs good on interstate. Have replaced, PCV, fuel filter, plugs wires 9 months ago, throttle position sensor, IAC valve sensor, EGR. Had it put on the scanner today. They said it showed a code for coolant temp sensor (and needed ECM ground under the hood worked on ?? not sure about this). I replaced the coolant temp sensor, now only stalls when a/c is off. Incidentally, the engine temp is running hotter now, about 190-220F, was running about 170F before coolant sensor change. Any advice would be appreciated. Thanks.