[Stl-986]

these are a pain to troubleshoot since they are random. But I doubt your issue is either of the above.


Need more information when it does it. Does it try to crank over and no start or does it not even crank over?
Do you have cruise control?
If it does crank over, does the tach move (even just a little bit)?

If it does crank over and tach does move, it's fuel pump or fuel relay
If it cranks but tach doesn't move, its the CPS
If it doesnt even crank, it could be the starter, starter relay, battery or terminals

cruise & brake switches are known to go bad and are cheap & easy to replace. Ignition is cheap but a pain to replace and another known item to cause issues like this, even random. Last thing I would think is the issue is the starter, but you already replaced that and the switch.

Answering the above when it happens will help. It isn't common that the relays would go bad in these unlike a 944 that the DME relays are very well known to go bad and almost anyone keeps a spare in the glovebox.