Tracker dies on road,engine light fades when accelerating

My sister has a 92 Tracker and she has a weird problem with the car. Sometimes the car dies on the road and her check engine light is on too that fades once she accelerates. Maybe even disappear. But at red light stop its back again.

Im thinking its the alternator that gives weird and uneven charge but is there any other guesses?

Thank you very much in advance

When that happened on my Porsche, it was a loose vacuum(spellcheck) hose, but I don't know alot about Trackers, so don't quote me.

thank you Ill look into that hopefully it is something simple!