Bought a 2004 Aveo second hand and felt like it was riding a bit rough. To me it felt like a transmission problem. Took it to a transmission specialist and though the ATF was dark he said the gears looked fine, the shift quality was good and then he began a process of slowly replacing the fluid over a few months time.
Now, my girlfriend's Yaris drives smoother than my Aveo and it's actually got about 20,000 more miles on it. Granted, I don't know as much about cars as I should, so what I think feels like a transmission problem could be something completely unrelated, and probably is since two transmission specialists have given the tranny the thumbs up.
But, when I drive my car it feels sluggish, and I notice the shifting in a way that I don't in my gf's Yaris. I'm probably being too vague but are there any thoughts out there about what could be wrong with my car? Could it be a fuel system issue? Air intake? I'm lost.