I have a 98 Taurus with a 3.0 ohv. It has 98k and runs fine except for every third friday afternoon it will crank but will not start for about 30 minutes. Then it starts and runs fine for three more weeks until the third friday afternoon then it repeats the same problem (3 times now). I have replaced the ignition switch, fuel filter and plug wires. I have not been able to test for fuel or spark when it won't run, by the time I get their its already restarted. Any ideas would be greatly appreciated.