Narrative:

Engine started acting rough. I asked ATC for nearest airport. I didn't feel I was getting all their attention so I declared an emergency. I did an ILS to richmond airport and landed safely. At the airport, I had a mechanic (actually 2) come from a nearby airport (no mechanic at field) and check plane out. He ran the engine and I flew a pattern with the (other mechanic). Engine was rough but when carburetor heat was pulled, the engine seemed to smooth out and RPM's came up. The mechanic said they thought the problem was carburetor ice. My intuition said it probably wasn't since the roughness was pretty sudden and I have a carburetor heat gauge which I make sure is in the green all the time. Also, I was not in visible moisture at the time of incident. I took off again and the engine ran a little better when I had carburetor heat applied, but on my climb to 5000 ft engine faltered badly, almost to the point of stopping. I then declared another emergency and redid another ILS into richmond, at which point I left it for the mechanic and rented a car. The mechanic called me and told me it was an exhaust valve that had gone and that he would be replacing the cylinder. I probably should not have taken off the second time even though I had 2 mechanics tell me that the engine was okay. In retrospect, my inner voice told me it was not carburetor ice because it was a sudden engine roughness, partial carburetor heat was on, and full carburetor heat did not solve the problem. My judgement to go on was based on the fact that I was 500 mi away from my home base and I had to be at work the next day.

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Original NASA ASRS Text

Title: DIVERSION TO ALTERNATE ARPT WITH FLT ASSIST AFTER EMER DECLARED WITH ROUGH ENG. ACFT EQUIP PROB.

Narrative: ENG STARTED ACTING ROUGH. I ASKED ATC FOR NEAREST ARPT. I DIDN'T FEEL I WAS GETTING ALL THEIR ATTN SO I DECLARED AN EMER. I DID AN ILS TO RICHMOND ARPT AND LANDED SAFELY. AT THE ARPT, I HAD A MECH (ACTUALLY 2) COME FROM A NEARBY ARPT (NO MECH AT FIELD) AND CHK PLANE OUT. HE RAN THE ENG AND I FLEW A PATTERN WITH THE (OTHER MECH). ENG WAS ROUGH BUT WHEN CARB HEAT WAS PULLED, THE ENG SEEMED TO SMOOTH OUT AND RPM'S CAME UP. THE MECH SAID THEY THOUGHT THE PROB WAS CARB ICE. MY INTUITION SAID IT PROBABLY WASN'T SINCE THE ROUGHNESS WAS PRETTY SUDDEN AND I HAVE A CARB HEAT GAUGE WHICH I MAKE SURE IS IN THE GREEN ALL THE TIME. ALSO, I WAS NOT IN VISIBLE MOISTURE AT THE TIME OF INCIDENT. I TOOK OFF AGAIN AND THE ENG RAN A LITTLE BETTER WHEN I HAD CARB HEAT APPLIED, BUT ON MY CLB TO 5000 FT ENG FALTERED BADLY, ALMOST TO THE POINT OF STOPPING. I THEN DECLARED ANOTHER EMER AND REDID ANOTHER ILS INTO RICHMOND, AT WHICH POINT I LEFT IT FOR THE MECH AND RENTED A CAR. THE MECH CALLED ME AND TOLD ME IT WAS AN EXHAUST VALVE THAT HAD GONE AND THAT HE WOULD BE REPLACING THE CYLINDER. I PROBABLY SHOULD NOT HAVE TAKEN OFF THE SECOND TIME EVEN THOUGH I HAD 2 MECHS TELL ME THAT THE ENG WAS OKAY. IN RETROSPECT, MY INNER VOICE TOLD ME IT WAS NOT CARB ICE BECAUSE IT WAS A SUDDEN ENG ROUGHNESS, PARTIAL CARB HEAT WAS ON, AND FULL CARB HEAT DID NOT SOLVE THE PROB. MY JUDGEMENT TO GO ON WAS BASED ON THE FACT THAT I WAS 500 MI AWAY FROM MY HOME BASE AND I HAD TO BE AT WORK THE NEXT DAY.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.