cannot believe it was written by an engineer (at Lyco) because why would the engine falter
Because fuel condensates on cold metal and the mixture does not ignite. That’s what they’re referring to.
Which parts would it be condensing on?
The initial parts are the fuel servo or the carb, and then you have the large mass of the aluminium casting which makes the sump / inlet manifold and these will take ages to warm up.
Also, if fuel was to be condensing there, that’s a lot of fuel that’s going somewhere (3 USG/hr for an IO540) and when it finally gets “liberated” it would make a big bang.
What’s the difference between this and the first turn of the starting motor doing the same thing?
Except on days of utter frustration (when one shouldn’t go flying anyway), my turning is gentler than the starter’s. 
Lycos need very rich fuel for some time after startup, some even require you to pump with the throttle. That is because of condensation. The condensed fuel goes into the oil through the piston rings mostly or exits as unburnt fuel through the exhaust manifold.
My O-320 C172 would require about 15 seconds of throttle pumping when starting at let’s say -10°C and a least one minute of full rich afterwards, otherwise the engine would die. Same for the PA28s I’ve flown. My TR182 doesn’t require any of this, it starts easily at all temperatures but if I lean the engine too early (let’s say 3 seconds after starting), it would die as well.
I have read
“Engine is warm enough for takeoff when the throttle can be opened without the engine faltering.”
in the past but cannot believe it was written by an engineer (at Lyco) because why would the engine falter, other than the internal grinding together so hard that the power produced by combustion cannot overcome their friction?
This wording is used in Piper manuals. Recent Cessna 172 manuals (also Lyco engine) use different words but the with same meaning:
“If the engine idles and accelerates smoothly, the airplane is ready for takeoff.”
then never change the throttle setting until the next start Quote
I’m not in agreement with this. The throttle is a control, and it’s proper operation should be checked before starting. One of the few times I have damaged a plane was because I did not do this check. Now every pre start check I do includes one full motion of the throttle.
How do you know, when you move the lever, that it actually does something with the throttle plate?
then never change the throttle setting until the next start
That’s like the woman that always parks the car in the garage with the gear put in reverse so she is ready for going out. Works fine until one day her husband parks the car…
Some people seem happy to go once the temperature is off the stops, others want it in the green arc (if there is a green arc). Some POH’s make a definative statement on this and some don’t.
Know your systems. If the transducer is located at the engine, you might get a green indication quite fast, whereas some old indicators do take their while to display a temperature, if the oil is cold and has to be transfered to the instrument. Our 172b even takes its 20 seconds to display any oil pressure. If I’d wait for the oil temperature to show anything, I’d propably have half the fuel burned before takeoff :-) And off course, this is a function of the oil used. Wintertime and a summer weight oil, like Aeroshell W100, it will take considerably longer for an ancient oil gauge to display anything than with a W80 or even a 15W40, which is thinner at lower temperatures. Plus, those instruments don’t have the ability to read engineering quality figures anyway.
I was thought to warm the engine at 800rpm. But the POH says to use 1500rpm.
Lycoming recommends not to idle the engine below 1000 rpm at all times to prevent lead fouling, especially in cold weather. More RPM is always hard on the bearings when the oil is thick and can’t be transported to the bearings. I assume the POH is one of Piper? I always thought the Piper engines take quite a beating because of unnecessary high RPM values in the POH. (The POH of our P28A speaks of 2000 RPM for the mag Check, while we normally use 1500 on the same engine in other installations.)
Most talk about letting the oil get warm and spread through the engine.
Keep in mind, that the engine takes in water through moist air and if not heated away properly, the engine will collect moisture in the crankcase and rocker boxes. Although this is more an issue with cold cruise oil temperatures, not so much at start up, when the oil will get hot and vaporises moisture during flight. But for that reason, cycling the prop every now and then in cold temperatures is a good idea during cruise. Just enough to get warm oil into the dome.
How do you know, when you move the lever, that it actually does something with the throttle plate?
Unless it’s completely disassembled, you feel any lose connection, or worse, any unusual friction, jamming, blocking or constraint in the lever. I once had experienced a lose prop lever and was unable to go back to fine pitch during final. Although I think it did loosen during flight, because I didn’t notice anything unusual while cycling the prop.
Re misfiring on acceleration when the engine is cold: my Lycoming doesn’t do that but then again I’ve never flown it in really cold weather. Mine starts and idles immediately with a couple of shots of prime and then once running I lean it almost immediately (in warmish ambient conditions).
My little Continental has a Stromberg carb with no accelerator pump, and the plane has no primer. In low ambient temps I pull it through with the throttle closed until the carb/manifold floods – i.e full dripping slightly out of the air box. Then once its started, which it always does pretty quickly, it needs a bit of warm up time before the throttle can be advanced smartly for take-off. The first time I got up really early and launched into cold weather this gave me a bit if a shock.
My motorcycles are similarly different. One of the old Italian bikes has to be ridden 15 minutes before it will idle smoothly – lots of cylinder head mass to warm up before the fuel will stay in suspension. The EFI bikes start and idle immediately with the warmup enrichment curves I’ve programmed experimentally. That’s great for utility but there is really something nice about the engine telling you how warm it is through warm up characteristics as it ‘wakes up’.
