Hi, Just wanted to add my two cents worth...
Having just seriously started flying pistons again, had something happen the other day that re enforced the importance of thinking about your conditions as a potential indicator as to what may be causing your problems.
We (I was instructin and the Stud was running the checks) were doing the run up and had checked Mags, Carb heat and inst and got to the idle check and the engine wouldn't idle, the RPM just continued to drop and would have stopped if I didn't crack the throttle slightly.
I though, hmm it didn't do this yesterday so we tried it several time with no change, I tried a static check and lo and behold it was a couple of hundred rpm low.
Everything else was fine so we set 1000 and thought about what could be causing this problem. Looked around and saw some low cloud around just off the hills and thought, wonder if it could be Carb ice. Ran it up to 1700 and gave it a good dose of heat, not the Hot-drop-Return that we had done before.
Tried the idle and it worked fine.
So to get back on topic, if you have a power loss or can't develop full power don't forget your Carb Heat (where applicable) and leave it hot while you run the rest of your checks as it may take a while to work.
It really surprised me that there were no other indications of a problem apart from the idle response and then with further investigation, not meeting the static numbers. Also checking the Carb heat (for operation rather than to clear ice) didn't indicate a problem.
Never to old to learn!