986 intermittent no start

[TSP]

I need to find some help. I have (actually my wife has) a 1997 Boxster. It is fast approaching 100k miles. For no discernible reason, it will sometimes do absolutely nothing when you turn the key. I have replaced all of the common culprits (switch on both brake and clutch pedals, starter, car battery, key battery) and checked the relays in the trunk by switching the two that are identical to make sure one of the relays isn’t intermittent. This thing is most annoying as it will go weeks and weeks where it starts and runs flawlessly and then one morning out of the blue, nothing. A couple cycles of the key and sometimes it fires (sometimes...), and sometimes it will start right up the next day. The thing is diving me completely nuts. I took it to a well known independent shop in Madison, WI and they thought the battery was weak and changed it out. That was last fall. This spring, it’s doing it again. It was on a trickler all winter in a heated garage, charging system is fine (14.2v out) and battery checks fine this spring as well. Any constructive advice would be greatly appreciated.

[JFP in PA]

You never mentioned the electrical section of the ignition switch, which is a common failure point in these cars..........

[TSP]

Yea, forgot to mention, but I replaced the ignition switch as well. Last season. Our host got quite a bit of business from me last year with one 986, one 356 and a 997.2 C4S as a daily... I’ll live in the middle of nowhere and my only independent that would work on these retired, so if I can’t fix it, it’s 4 1/2 hours south to the nearest dealer or independent.
Tim

[Dick Shift]

Crankshaft Reference Mark Sensor - Bosch 0-261-210-204
Often cause starting / running problems. With that kind of millage not a bad idea to replace for sooner or later it will fail.