1989 944na with 70K miles. When at operating temp, Engine will not start maybe 1 out of 10 times. If I jiggle the reference sensor cable Connector near the firewall, pushing male and female plugs together, engine starts fine. Connectors look fine. Is this a common ? Is there a simple fix?

 

Clean grounds and all other connectors contact cleaner, also bottom of fuse box. Maybe time for a new DME relay for you ?