INFLT ENG SHUTDOWN.

Narrative

AFTER LEAVING OUR DEP ARPT; WE LEVELED AT 7000 FT FOR A SHORT IFR FLT TO EKM. SHORTLY AFTER LEVELOFF; WE NOTED A SLIGHT 'HOT' ODOR WHICH I ASSOCIATED WITH ELECTRIC HEAT WHICH HAD BEEN IN USE ON THE GND. I TURNED OFF THE MODE CTL; BUT THAT DIDN'T SOLVE THE PROB. NEXT I TURNED OFF THE BLEED AIR VALVES (1 AT A TIME) TO ISOLATE THE SOURCE. BY THIS TIME WE WERE WITHIN 25 MI OF EKM -- ABOUT 9 MINS FLYING TIME. THEN THE L OIL PRESSURE GAUGE BEGAN TO SLOWLY FLUCTUATE ABOUT PLUS OR MINUS 5 PSI. AFTER A FEW MINS; THE PRESSURE STARTED TO SLOWLY DROP. BY NOW WE HAD THOROUGHLY EXAMINED THE PERTINENT AREAS OF THE EMER CHKLIST. WHEN THE PRESSURE REACHED ABOUT 65 LBS; WE HAD BEEN CLRED TO LAND AND WERE ABOUT 6 MI FROM THE ARPT. NEVER-THE-LESS; I MADE A PRECAUTIONARY SHUTDOWN OF THE L ENG. WHEN I OPENED THE LEFT COWLING; I WAS SURPRISED TO FIND THE OIL DIPSTICK UNLOCKED -- SOMETHING I'M VERY CAREFUL ABOUT DOUBLE CHKING AS BEING LOCKED. SOMEHOW I DID NOT GET THE LOCKING CAP FLUSH DOWN AND THE ENSUING VIBRATION CAUSED IT TO BECOME COMPLETELY UNLOCKED. IT LOOKS LIKE I'LL NEED TO TRIPLE CHK IT AS LOCKED NEXT TIME.