Yukon Will Not Start...again

[ncmoore4]

Hello-

We have a 2003 Yukon (5.3 flex engine) with 73K miles. Two years ago at 53K miles it would not start after sitting in the garage for the weekend. We had it towed to the dealer and they found/replaced a shorted out throttle body. After $800 it was fixed and we've not had a problem till recently. I'll mention that before this happened I replaced the fuel filter and then the intake gaskets due to a leak in the original gaskets between the intake and the heads. We have never ran E85, just normal pump gas. About a month ago we went to start it after sitting in the garage for the weekend and it would not start. The exact same problem as before at 53K miles. It turns over just fine but then stops and sounds like the TBody is not opening...like it cannot get air into the engine. This time the DIC displayed a "Low engine power" message when trying to start it. For the heck of it I removed the battery and had it checked at Auto Zone and it was fine (it's a couple of years old). When I put it back in two hours later and after trying it a few times it started up and has been fine every day for a month. No rough idle, no problems at all starting at least twice a day. Now for a third time it would not start after sitting in the garage for the weekend. So, I disconnected the battery again for a day with no luck this time. I also went ahead and replaced the throttle body today (reman from O-Reilly) trying to save some $$. It still will not start! I'd like to fix it myself and prevent a tow to the dealer and another $800 bill. Since I was able to get it running last time by removing the battery, I figure this is some computer/programming problem but what do I know? I do know I have three instances where it sits in the garage for two days and then has the same problem each time so there is some consistency with this one. Before this weekend I thought that the previous TB replacement at the dealer was not necessary and thought I had saved $800. Now that it's doing the same thing, I'm stumped! I not sure yet but I'm doubting that it's a fuel delivery problem. We ordered and bought this truck brand new and it's basically still brand new except for the mileage. Well taken care of, no mods, and in prestine condition. Any ideas? Anyone heard of this before? Thank You!