Hello,
I have a 2007 Tahoe LT with about 120k miles. I recently bought this truck, and something that I did not notice until after the purchase was the start up issue it had. When the truck is cold, and I start it, it stumbles for 3-5 seconds. It also seems to take longer than it should for the oil pressure to build up on the dash gauge. It still does this on a warm start, but it goes away much quicker. I scanned for codes, but there was nothing. According to my scanner, coolant temp data seemed to be accurate. I also checked for vacuum leaks, but nothing. I will be testing the fuel pressure later, but I don't think that is the issue since it runs fine and has plenty of power aside from immediately after start up. At this point I am at a loss for what it could be, so I'm hoping someone has experience something similar.

 

try this: clean the throttle body and then perform an idle relearn procedure.