My gmc envoy 05 running rough

loose/broken vacuum lines , fouled injectors , EGR function , some vehicles are particular about fuel pressure , just having it doesn't always do it .

Just to add, I saw some service bulletins for 4.2L engine, rough idle and miss-fire. There were several. Any applicable trouble codes to lead us in the right direction? I also noticed you have tac/throttle actuator control, You could take an old tooth brush and scrub the throttle bore and throttle plate, to see if it helps? Don't force throttle plate. The basics for a rough idle, check for a leak of some kind, fuel--egr--vacuum leak, as my friend has mentioned. Some libraries have automotive databases, you get wiring diagrams--service bulletins, just about everything. It's free if you live in the area they serve, may not be the best, but, better than nothing. Just my opinion.

Hi there! Most popular would be a filthy throttle body. Disconnect fuses #10 and #28 under the hood, then remove throttle body to clean both sides. 2nd thing especially at a stop, would be motor mounts. Our motor mounts are hydraulic, so very hard to tell if they're bad. With a clean throttle body, and it still idles bad at a stop, replace the mounts with AC Delco's ONLY! Other brands will crush prematurely, leaving you where you started.