1990 Geo Prizm GSi rough idle

I took my car to my mechanic for a rough idle and stalling problem in stop and go traffic. Diagnosis - head gasket leak. Following a head job, new piston rings, rod and main bearings, vacuum switching valve, cold start injector, and thermostat the car still experiences the same problem. Car runs great at highway speed with great acceleration. I am normally happy with my mechanics work but do want to get an opinion in advance before I go back.

Yeowsa! Rebuilt the top half of the engine and it STILL acts up.

If I were you, I’d look for a better mechanic. Get another opinion.