I have a 2003 Nissan Micra 1.2 that has recently been giving trouble. At first, it was just kangarooing for 30 seconds after moving off, then it got worse and would do it for maybe a minute or two. More recently, the engine would start cutting out on starting and would only go if you rev the engine a little. Then, sometimes it would even cut out at 6000 rpm. I have now found that it starts okay if you rev and then take off immediately.

There are no lights on the dash to suggest any faults. I had a basic service done this week, so spark plugs and air filter were replaced. I took the car to the mechanic who ran diagnostics and a few faults were coming up. They were cleared and test was run again and an unknown code P0340 came up again. I found this related to the camshaft position sensor, so the mechanic suggested replacing this as the easiest and cheapest option. Unfortunately, this didn't do anything for the car and the code was still present on the next check. What's wrong?