EXPERIMENTAL ACFT HAS PWR LOSS AT CRUISE.

Narrative

WHILE CRUISING AT 4500 FT MSL. I ADDED PWR TO ADJUST MY ALT. I WAS ACTUALLY 100 FT LOWER THAN 4500 AND WANTED TO GET BACK UP. WHEN I PUSHED THE THROTTLE IN; THE ENG FALTERED AND LOST PWR. UPON RETRACTING THE THROTTLE TO THE ORIGINAL SETTING; THE ENG REGAINED THAT PWR; AFTER A COUPLE MORE ATTEMPTS WERE MADE TO ADJUST PWR; I FOUND THAT IF I RETRACTED PWR I COULD NOT GAIN IT BACK. GIVEN THE HIGH HUMIDITY AND THE FACT THAT ALL OF THE ENG MONITORING INSTS WERE NORMAL; I FELT I WAS EXPERIENCING ICE BUILD-UP IN THE INTAKE SYS. NOT HAVING CARB HEAT. I DECIDED TO MAKE AN EMER LNDG AT THE NEAREST RWY WHICH WAS JACKSON; ABOUT 4 MI TO THE E. WITHOUT RADIO; I INTERMITTENTLY ACTIVATED MY ELT AS I DSNDED TO THE ARPT; IN AN ATTEMPT TO ATTRACT ATTN. AS I APCHED THE RWY I PICKED UP THE DEPARTING TFC AND MADE SURE TO STAY CLR AND WAS ABLE TO LAND BTWN DEPARTING AND LNDG ACFT WITHOUT ENDANGERING ANYONE; AND EXITED THE RWY INTO THE GRASS IMMEDIATELY. THE TWR PERSONNEL DID NOT EVEN KNOW I LANDED UNTIL THE FBO CALLED THEM ASKING IF THEY WERE AWARE OF ME. I WENT UP AND SPOKE WITH THEM EXPLAINING MYSELF AS I HAVE DONE HERE. I FEEL THAT THE HIGH HUMIDITY ON THAT PARTICULAR DAY CAUSED ICE BUILDUP IN THE INTAKE SYS. I'VE FLOWN THE ACFT FOR 140 HRS SINCE 1988; AND HAVE HAD NO PROBS AS SUCH; BUT I DON'T RECALL EVERY FLYING IN SUCH HUMID CONDITIONS. THE PLANE WAS STARTED ABOUT 5 MINS AFTER LNDG. IT RAN ROUGH FOR ABOUT THE FIRST 30 SECONDS OF ADDING THROTTLE; WENT BACK DOWN AND ADDED THROTTLE A SECOND TIME. THE ENG ATTAINED AND MAINTAINED ITS NORMAL STATIC RPM; THIS WAS REPEATED 3 TIMES. BECAUSE OF THE HEAT; I PULLED THE ACFT INTO A HANGAR ON THE FIELD; DECOWLED IT; AND GAVE IT A THOROUGH LOOKING OVER; FINDING NOTHING UNUSUAL. I STARTED AND TAXIED THE PLANE OUT AND FLEW IT HOME LATER THAT EVENING WHEN THE TEMP COOLED DOWN. WITH THE TWR'S PERMISSION AND LIGHT SIGNALS I TOOK OFF AND CLBED OVER THE RWY TO 5000 FT MSL. WHEN ALL SEEMED WELL; I WAGGED MY WINGS AND DEPARTED TO THE E FOR METTETAL ARPT; THE CRAFTS HOME BASE. THE FLT BACK WAS UNEVENTFUL. I AM CURRENTLY WORKING ON A WAY TO INDUCE WARM AIR TO THE CARB WHEN NEEDED; TO HOPEFULLY AVOID SUCH A SIT AGAIN. AT 4500 FT MSL AND THE ENG STILL ABLE TO PRODUCE PWR; I BRIEFLY THOUGHT OF TRYING TO MAKE IT TO AN UNCTLED FIELD; BUT DECIDED AGAINST IT KNOWING FOR CERTAIN I COULD MAKE JACKSON.