Fiesta Finesse Engine Management Light

[RACAFC]

 Hello folks, just picking your brains here. I have a high mileage petrol Finesse & the EML has come on. The result is a juddery start & when accelerating from still. There is some loss of power going uphill, but at cruising speed it travels as well as it did before the light came on. All fluid / oil levels are ok. As it's an old car I'm loathe to spend much on it for repairs, I'd sooner buy another one if it's a major problem. Can anyone suggest what it may be so I can try remedial action myself before taking to a garage? Thanks