N63886, a privately operated PA-23-250 aircraft, was taking off from Runway 06 at Sydney/J.A. Douglas McCurdy, NS (CYQY) for a local flight. On departure, exhaust gas and cylinder head temperatures dropped suddenly on the number 4 cylinder of the number 2 engine. The pilot initiated a left turn to return to the airport and made a PAN PAN call. ATS suggested a landing on Runway 18, and the aircraft landed without further incident.
A post flight inspection revealed a broken engine ignition lead for the number 4 cylinder of the number 2 engine.