Bike: 2003 Specialized Sequoia Sport, Sora triple FD. Currently has 1250 miles on it and worked flawlessly for the first 1200 miles. Just last week I started having problems getting onto my big chain ring. At first, I'd just have to hold the lever over for a bit and eventually it would shift. Then I'd have to really push and it would go and lastly it just wouldn't shift at all (it would click into position but the chain wouldn't move and I'd have to click it back down). This progression took place over that last 50 miles. I ride mostly on the middle chain ring so this problem only occurred about 3 times during my 20 mile morning rides. Shifting to the small ring was never a problem.

My background is that I'm very experienced working on cars (mechanical engineer as a profession) but I have no experience tuning bikes. When looking at the front cage during the shift, it looked as though it was not moving far enough towards the big ring to complete the shift. This was also evidenced by the rubbing I would get while using the middle ring and the smaller rings on the rear hub. I read through Barnett's sections on front derailleurs and tried adding some tension which helped the rubbing in the middle ring but still did not help me get into the big ring. I then tried to make a larger adjustment by loosening the cable pinch screw and pulling more cable through. This is where things went really wrong. Suddenly, I could not shift at all. It was like my levers lost their detents. Being overly inquisitive, I decided to try and disassemble them a bit and see if I could find anything obviously wrong. What I did find was that if I released all tension from the levers, functioned them a few times, they would eventually start to click into their detents again. I then remounted them, clicked them a few times, and just like they reappeared, the detents were gone again and I could not shift.

So my question is, are my shifters/derailleur bad or am I just completely lost as to how to tune these things? I'm going to feel pretty dumb if I'm just adjusting them wrong (I think they must be broken) but I'll feel even more dumb if I buy new stuff only to have the same problem. Oh and by the way, I like doing everything myself so dropping it off at the LBS is only a last resort option. Then again, I really want to ride this week so I'd like to get this sorted out quickly. Thanks for any help.