I took the old girl out for her first real trip last weekend, and it was a great success. No majors, only a moderate list of minors to resolve. We did over 1000 miles and hardly a hiccup. The 6.0 LS is such an awesome motor and it really wakes the rig up. Doubling the HP and getting better fuel economy is a win-win. Across the board I got 3 mpg better than the 1FZ it replaced. I am not sure how bad off my 1FZ was, but when the current owner of it did a tear down, the #5&6 pistons were pretty bad off. The best I ever managed out of it was 13.5 mpg and I got 16.5 mpg on the leg from Flagstaff to the South Rim and around. That was mainly cruising at 55 mph or so, and it was very happy to lope along in 6th gear at low rpm. Once out on the highway at higher speeds, the mileage dropped off a good bit, and it averaged about 13 climbing the hills from Phoenix to Flagstaff, and from Page to the North Rim. The plus is that it can do it at 75 mph now, so if I had the patience to be calm and keep the speeds low, it'd get better mileage. One serious complaint I have, which is the same on most the GM trucks I have ever driven is that the cruiser control is too aggressive. If speeds drop 5 mph the dang thing will shift from 6th to 4th, or even third and rocket off to get back to speed. I looked over and the tach read 5200 rpm once. Not a pleasant sight. Another note, is that I installed a Mark's Part Time kit. I have no way to tell if it made a difference in mileage, but by god it makes it so much better to drive. The trade off is that I had to get out and lock the hubs when I couldn't pull out of some muddy ruts in 2WD, but that is a small price for how much better it drives. Overall it was an absolutely fantastic weekend and the sights, the drives, the food, and the company was much appreciated. Thanks Rod, Marlotta, and
@D_Web.
The only hiccup with the rig was coming back down into Flagstaff. After coasting down for a few miles and just getting to the city limits, the check engine light came on and I lost throttle control. The engine went to idle and I coasted off the road and came to a stop. I checked the codes and I had a "Bank 1 Too Lean" and a "Throttle Voltage Correlation Error". We had seen the 2nd one before, and a quick check of all the throttle connections revealed that the connection to the throttle pedal had backed off. I checked it, pushed it on until it clicked, cleared the codes, key cycled it, and it came to life and hasn't faltered since.