kh laser 1.8 sohc idle surge

[BigCav]

Hi guys

I'v just bought a first car for my brother, a 1991 ford laser s 1.8 sohc

now i absolutely love the car, almost dont want to give it too him haha



but i do have a single issue, the engine will randomly hunt/surge from idle

makes 1/10th of ****** difference when driving but when your at the lights or puttering around its really annoying and embarrasing

will idle fine at around 1000 rpm or so, and will jump up to 1800-2000rpm for no reason

is this common? easy fix?


previous owner said it was the airflow meter but i fail to see how this would affect it enough at idle, im more inclined to think coolant sensor or something?

does the ecu have a self diagnosis function? if so how do i read the codes etc?