Engine Performance problem
1991 Pontiac Tempest 6 cyl Front Wheel Drive Automatic 155000 miles
When my car warms up it sporadically stalls when at a stop in drive. It has a rough idle when warm as well. If I put it into nuetral when at a stop it is fine.(Little rough but not as bad). This only happens when it heats up. I will be replacing the theramostat, but doubt will be the solution. I have replaced the crankcase sensor which did not change anything. Help.