I tend to BPF's view, engines usually try and tell you they are not happy, even when something occurs during a flight a partial power loss, albeit sometimes a considerable level are the most common effects.

I've had three serious engine problems in just under 30 years, all of them the engine kept running - although in one case very unhappily.

Emeraude - fuel pump failure, fuel would reach the engine whenever the nose was lowered - at least it gave me some options!
Terrier - cylinder head cracked, engine would run at 1700 rpm max, very lumpy but made me quite a good glider!
Terrier - cylinder crack, 1700 rpm again...

Equally at our airfield I've seen people 'flight test' engines with issues and then get very sweaty when the faults were still present!