Narrative:

I was the PIC flying inland and upon reaching the shoreline; approximately 5 NM from my destination; I noticed that the tachometer was malfunctioning reading near zero. Very shortly after noticing this issue; there was a noticeable surge of engine RPM; and a very noticeable vibration. I reported to approach that I was experiencing a propeller run away situation; which I thought was related to the malfunctioning tachometer. I did not report an emergency; but requested priority handling. I adjusted the controls to what I thought was a propeller runaway situation; but then noticed that the egt and cht indications for cylinder number 3 were dropping past normal operating ranges. That is when I realized that the tachometer issue I was experiencing was completely unrelated. At this point I realized that the vibration I was feeling from the engine; and lack of performance; was due most likely to a malfunctioning cylinder valve. At this point I informed approach that I would be officially declaring an emergency; and would need to be kept at my current altitude until 2 NM from the landing runway. Once there; I was given a turn to base; and given a landing clearance. The rest of the flight ended without further incident; no fire; no injury; and no further damage to my aircraft or other aircraft. A statement was given to doa and the fire department.

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Original NASA ASRS Text

Title: A PA-32 tachometer was indicating near zero when the engine began surging along with a vibration. After troubleshooting the pilot realized that probably a cylinder valve malfunctioned; so he declared an emergency near his destination airport.

Narrative: I was the PIC flying inland and upon reaching the shoreline; approximately 5 NM from my destination; I noticed that the Tachometer was malfunctioning reading near zero. Very shortly after noticing this issue; there was a noticeable surge of engine RPM; and a very noticeable vibration. I reported to Approach that I was experiencing a propeller run away situation; which I thought was related to the malfunctioning Tachometer. I did not report an emergency; but requested priority handling. I adjusted the controls to what I thought was a propeller runaway situation; but then noticed that the EGT and CHT indications for cylinder Number 3 were dropping past normal operating ranges. That is when I realized that the Tachometer issue I was experiencing was completely unrelated. At this point I realized that the vibration I was feeling from the engine; and lack of performance; was due most likely to a malfunctioning cylinder valve. At this point I informed Approach that I would be officially declaring an emergency; and would need to be kept at my current altitude until 2 NM from the landing runway. Once there; I was given a turn to base; and given a landing clearance. The rest of the flight ended without further incident; no fire; no injury; and no further damage to my aircraft or other aircraft. A statement was given to DOA and the fire department.

Data retrieved from NASA's ASRS site 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.