A friend of mine who you helped with his Lincoln gave me your name. I also have a Lincoln LS, year 2005 with the V8. I have a couple of problems that I need to take it back to the dealer for. I've had it there before but they tell me that they could not find any problems.
I have a hard start in the mornings, sometimes taking twice to start it. It was fine and then one day it started getting worse and has been that way for some time now. It is kept outside all the time.
The second problem is when I am coming to a rolling stop, as to a side street or stop sign. It hesitates when I give it gas to go. A few seconds later it takes off. Quite a few times I just about got rear ended.
Nothing's really staring me in the face. The hard-start and hesitation may be fuel pressure related, or the result of a number of other possible faults. These could be ignition problems, a glitch in the throttle position or mass airflow sensor, the lack an updated calibration for the powertrain control module (the brain behind it all), and so on and so forth.
Even the transmission not downshifting quickly enough could imitate a hesitation when taking off from a near-stop. Give your Lincoln service department a second chance and casually mention all of the above. The technician might have come up empty on the initial road test, and therefore never took the next step in testing.
One item did catch my eye while browsing the '05 Lincoln service data, probably because you mentioned your LS spending a lot of time outdoors. A few LS with the 3.9-liter engine have been the victim of water intrusion. A water leak at a foam seal for the cowl panel grill (between the windshield and the engine compartment) may flow down to the top of the engine and enter the ignition coil wells. That's where the ignition coils sit right on top of the spark plugs.
This condition can cause misfires, trouble codes, and who knows what else. The correction is detailed in Lincoln technical service bulletin # 05-16-2. May not be an issue, but interesting nonetheless.