erattic tick over

 just a general question to everyone my primera 2ltr diesel will only start when i push throttle down the engine managment light stays on until engine is up to normal running temp. until then it will not idle smoothly and will cut out when comming to a stand at a junction . i would discribe as a surging sensation.there is no loss of power when driving and my mpg is good ,ounce it,s up to normal running temp the engine ticks over normal and engine light goes out .i have changed fuel filter and done an oil and filter change . i,m a mechanic by trade and electrician totally bafelledany ideas ??????

it,s a primera td 2ltr gx 5 door deisel done 133k on a p plate tick over surges and engine light flickers in time with surge until warm then rights itself will then stall when stopping at junctions. couldit be a faulty sensor of some kind????

is a maf sensor an air flow sensor on the air intake

thanks for that mate will take a look at it will get back to you if i am sucessful choo choo