M20P PLT LOST SITUATIONAL AWARENESS WHEN BEGINNING APCH AT PRB.

Narrative

WHILE DISTR BY SEVERAL MECHANICAL PROBS; AND WITH ICING FORECAST AT OUR ALT S OF OUR POS; I ELECTED TO MAKE A PRECAUTIONARY LNDG AT PRB; RATHER THAN AIR FILE AN IFR FLT PLAN AND CONTINUE ON TO OUR DEST. I ASKED FOR AND RECEIVED A POP-UP IFR CLRNC TO THE FIELD AND WAS INSTRUCTED TO FLY DIRECT PRB IN VFR. THE UNDERCAST TOPS WERE APPROX 5500 FT MSL. WE WERE SEBOUND IN VFR AT 9500 FT. I DSNDED TO APPROX 7000 FT AND WAS DIRECT PRB VOR. IN MY ANXIETY TO TROUBLESHOOT THE MECHANICAL PROBS; INCLUDING A FAULTY FUEL GAUGE AND ENG SURGING; I MISREAD THE APCH PLATE FOR THE RWY 19 VOR DME APCH AND LOST SITUATIONAL AWARENESS. ARRIVING AT THE VOR AT 6500 FT; I ASKED FOR AND RECEIVED THE APCH CLRNC; WHICH WOULD HAVE NECESSITATED A 180 DEG TURN TO FLY OUTBOUND ON THE INBOUND RADIAL. I SHOULD HAVE TOLD THE CTLR AT ZOA THAT I DECLINED THE CLRNC; BUT; DISTR AS I WAS; I INTERCEPTED THE 192 DEG RADIAL AND FLEW OUTBOUND ON THAT HDG AWAY FROM THE ARPT. WHEN ASKED BY ZOA WHERE I THOUGHT I WAS GOING; I TOLD THEM OF THE ENG TROUBLES; AND RECEIVED VECTORS TO THE VOR FROM MY POS. THERE WAS NO DANGER. I NEVER DSNDED BELOW 5500 FT. THE MEA ON THE INBOUND LEG IS 4000 FT. DSNDING INTO THE CLOUDS; THE ENG STARTED TO SURGE AND I CANCELED THE APCH. AFTER CLBING INTO VFR CONDITIONS; I ASKED FOR VECTORS TO THE NEAREST VFR ARPT; KING CITY; CA. I GOT THE ENG SMOOTHED OUT AND PROCEEDED WITHOUT INCIDENT TO THE FIELD; ALTHOUGH THE ELEVATOR TRIM REMAINED JAMMED IN THE NOSE DOWN POS. AFTER ARR; IT WAS DETERMINED THAT THE SURGING WAS PROBABLY CAUSED BY CHANGES IN OIL PRESSURE; IN TURN CAUSED BY A FAULTY FITTING IN THE OIL SYS OF THE NEWLY OVERHAULED ENG.