Thanks for your answers to this question, however the solution must remain a mystery since a friendly local very helpfully decided to solve this problem for me by stealing the car and totaling it 3 blocks over. Thanks anyway guys.
I have a 2004 Mazda Demio (Mazda 2 with more letters) that's sitting above 200,000 km.
In the last month or so it's started idling quite rough, but is otherwise running ok-ish.
It's never had much go, and sometimes when you plant boot and try to move quickly into traffic from a stop sign it'll just refuse and limp out like I was pushing it... then it'll lurch off and pick up speed quite quickly once I'e already bothered everybody in my lane.
When I first bought the car (2nd hand in 2011) there was an electrical bug that caused the check engine light to come on for no reason, and the dealer has fixed it twice since for the same reason, but I now live at the other end of the country and it's past any warranty I would've had from the local dealer anyway. The light has only just popped back on, so I want to get it checked, but I'm hoping it's unrelated to the 2 stroke sounding engine I have now.
Real Question is, are there common or easily fixable reasons for the change in my cars idling that won't cost me hundreds to fix?