1998 Other Chevrolet Models 1998 Saturn SL2

The car starts and runs good for 5 to 10 minuets then shuts off. I have checked the spark when it shuts down and there is on spark. I replaced the ignititon module coils and spark plug wires and it still shuts down. I noticed when driving the car the engine rpm spike @ 750 rpms befors it dies. After @ 15 minuets it restarts and will drive and when it spikes in rpm again and you shift to neutral the engine rpm is at @ 3000 but will stay running and when the rpms go down you can shift back into drive for a few minuet. The timing chain went bad before this problem but was replaced with all the teninsioner hardware. The car runs at just below half on the temp gage and runs for over 45 minuets in park at idle. Any help would be greatly appreciated. Thank you Jeff