99 Deville cuts out at low rpm when hot
 

Car cuts out at idle or running, from time to time, between 1500 rpms and 650 when hot - above 217 degrees. When it happens the rpms drop to 350 and then cuts out. On start up it reeves to 3000 rpms and drops slowly to normal. Have changed the crank sensors and the mass airflow sensor (OEM) Also Catalytic convertor plugs and wires. Have had the coils checked. If sit at idle in neutral when hot the rpms cycle between 650 and 1200 about 6 times per minute until the car cools.