Was it sputtering and running rough before the coolant started leaking? If so i woukld say you just need a good tune up. Spark plugs, dist cap and rotor and maybe plug wires.
If it just started doing this after he worked on it then I would suspect he accidently knocked a sensor wire loose or broke a sensor plug in or knocked a vacuum hose off. Check all the electrical connections and vacuum hoses you can find and make sure they are tight.
This answer was edited by Monogyny644 19 days ago.
Reason: additional info
