1993 Other Nissan Models Nissan Micra GLX 1.3 manual - Multi

My micra has been suffering issues with cutting out when the clutch is depressed i.E. When going to idle. The revs sometimes drop to about 200rpm or less and the engine runs very roughly and often cuts. When driving, a similar problem intermittently occurs with very rough running and very poor fuel economy. When at a standstill, the exhaust smells very rich with unburnt fuel. I have done all the usual bits, i.E. Changed plugs, filters etc. To no avail. The self diagnostic test appears not to function on this car. Any thoughts? Many thanks. R