I'm relatively new to this whole bike mechanic thing, so I hope I have that right...the two pulleys (same size, tooth count) inside the cage hanging on the rear derailleur...cage pulleys, no?
Anyway, on my commuter bike (Gary Fisher Tassajara, pre-buyout, non-suspended) this morning, I was having difficulty shifting the rear. If I wanted to downshift to 5, say, I'd have to hold the shifter (these are GripShifters...yeah, I know ) in between 4 and 5 for the chain to move over. If I wanted to upshift to 6, I'd have to go to 6.5. On top of that, I tried shifting the chainring from the middle, which is where I almost always ride to the smallest ring. It rubbed on the front derailleur something fierce. To get to the biggest chainring, I had to actually overshift past 3, and then once the chain got there, it too rubbed like mad...just on the outside plate. The rear shifter 'trimming' thing has been going on a while, but I never paid much attention to it, as I tend to only use three gears and even then I spend most of my commute in one.
So, on the way home from work today, my drivetrain decided that a) it didn't want to obey and shifting commands for the rear and b) it would periodically, yet randomly, 'skip' resulting in the chain hunting between 4 and 5.
Tonight, I cleaned everything (Palmolive and warm water) as it was pretty gunked up (all that commuting). It doesn't look like there are any broken, missing or wildly bent teeth on any of the chainrings or cogs. So, I adjusted the front derailleur so I can use all three chainrings without the chain rubbing (although extreme cross-chaining still gets me some grinding action). With that done, I adjusted the limits on the rear derailleur and tightened up the cable a bit thinking it had stretched.
Now I have fairly responsive and more-or-less accurate shifting front and rear. But, occasionally, the chain will 'skip' and the whole cage will sort of catch and spring forward just a hair before releasing. It doesn't look like there are any teeth missing or bent on either of the cage pulleys, so I'm not sure why it's skipping. I did re-lube everything with some sort of Giant PTFE dry lube stuff that the LBS had given me a year or two ago.
Any thoughts or suggestions on which screw to turn next would be appreciated. OTOH, I almost always run my commute in the middle chainring and either 5-6-7 on the rear. Anyone know what my options are/the difficulty level is of swapping out this mixed Shimano grab-bag drivetrain. No sense carrying around a couple extra chainrings and cogs if I'm not going to use them.
You know, I really didn't check the chain out much at all. Told you I was a neophyte. It's too late to do it tonight, so I'll have to go easy on it for tomorrow's commute and check it tomorrow evening. Thanks for the suggestion.
I know you said you relubed; did you get the pivot points on the derailleur? Your problem sounds like friction somewhere in the system, either at the derailleur or cables and housing, as suggested above. Lube it all.