My wife's car, 2008 Nissan Micra/March 1.2. Imported from Japan, if that makes a difference.
Roughly 1/2 the time, the car won't kick down into passing gear. From a stop, the car goes through 1st, 2nd, 3rd gear fine and seems to have a normal amount of power. Upon merging onto the highway or approaching a hill, the car doesn't want to drop gears. I can put my foot all the way to the floor and the engine just lugs along, slowly picking up speed.
I've done a bit of preliminary research, and the throttle seems to be electronic. I don't know a lot about how this is supposed to work, but I would expect the computer would sense the engine RPM and throttle setting, and signal the transmission to change gear. Is this how it works?
She had it at the mechanics over the weekend, and he changed the catalytic converter in an attempt to fix this. I don't understand why he would think that's related to this problem, or how that would fix it. I think he's misunderstanding the issue as a general lack of power, and saw it was "clogged up". I'm a bit confused.
Any help is much appreciated.