Join Date: Sep 2011
Location: Cincinnati, Ohio
Bikes: '74 Schwinn Le Tour (x2), '83 Bianchi, '96 Trek 820, '96 Trek 470, '99 Xmart Squishy Bike, '03 Giant Cypress
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Hopefully there is nothing actually wrong... older brifters seem to be notorious for symptoms like you describe. The culprit is usually that the original grease from Shimano has hardened and stopped-up the mechanism. Some quick Googling will illustrate this.
Take the brifter off the handlebar, remove the hood and spray the heck out of the innards of the shifter with WD40, PB Blaster, or any other penetrating/"cleaning" type of spray. Use a lot... like half a can or more might be necessary. Work the lever/shift mechanism back-and-forth a lot of times during and after spraying it with the WD40. After you have (hopefully) freed-up the mechanism, then spray a ton of your favorite lubricant in there.