C152 PLT HAS MALFUNCTIONING ENG; REQUESTS CLRNC TO NEAREST ARPT; HAS ALT EXCURSION AND LANDS AT BMT.

Narrative

ON FEB/SAT/03; I WAS ON AN IFR FLT PLAN FROM CLL TO LCH WHEN I EXPERIENCED A SUDDEN LOSS OF ENG RPM. I APPLIED CARB HEAT; PUT THE MIXTURE FULL RICH; AND CHKED MY MAGNETOS. THE OIL PRESSURE AND TEMP WERE NORMAL AND THERE WAS NO SMOKE FROM THE ENG. MY EFFORTS HAD NO EFFECT IN RESTORING THE RPM TO NORMAL. I CONTACTED BEAUMONT APCH AND NOTIFIED THEM I HAD PARTIAL LOSS OF PWR FROM MY ENG AND THAT I NEEDED TO LAND. I ASKED FOR BMT AND THEN BPT WHEN I REALIZED THERE WAS IMC BELOW ME AND THE ILS AT BPT MIGHT BE NEEDED. ENRTE TO BPT; I SAW BMT THROUGH A BREAK IN THE CLOUDS. I ASKED ATC FOR CLRNC TO LAND AT BMT INFORMING THEM THAT I HAD THAT ARPT IN SIGHT. I SAID I WANTED TO CIRCLE DOWN THROUGH THE CLOUDS AND LAND AT BMT. DURING THIS TIME MY ENG RPM WAS VARYING AND I WAS AFRAID I COULD LOSE ALL PWR. I WAS GIVEN CLRNC TO BMT BUT GIVEN 3000 FT ALT ASSIGNMENT AND THEN APPARENTLY A 1600 FT ALT ASSIGNMENT. I UNDERSTOOD THAT I WAS CLRED TO LAND AT THE ARPT BUT WHEN I REACHED 1500 FT; BEAUMONT APCH SAID I BUSTED MY ASSIGNED ALT. I WAS ABLE TO CLB TO 1600 FT AGAIN AND THEN WAS CLRED TO CHANGE FREQ AND LAND. I DID NOT DECLARE AN EMER. ON THE GND; I DISCOVERED THAT 4 OF MY SPARK PLUGS HAD SEVERE LEAD FOULING.