Please remain on these treads! Your feedback is always excellent!!
Cold weather can take 10-15 minutes of 1,000 rpm running to see 100 degrees.
You can speed up the warm-up by using a higher RPM than 1000 within the Lycoming/Continental-recommended warm-up range of 1000-1200 RPM.
Does it require and engine to be warmed up? This is a magneto check right? The questions is does the check just need to be done just before take off or can it be done sometime after start?
You can also detect a fouled plug during the initial part of the takeoff roll by watching your engine monitor for all EGTs to rise together on initial throttle application. You do have an engine monitor don't you. ;-). For those who don't believe in such things, a $3k engine monitor just might save you a $30k engine or maybe your life someday, quite a positive cost benefit.
While I'm a strong proponent of engine monitors, I don't like the idea of trying to check EGT's after brake release -- it could be a distraction from maintaining directional control. You can get around this by lining up, holding the brakes, and running up to your run-up RPM and checking the EGT's (along with MP, RPM, fuel flow/pressure, temps, etc.) before releasing brakes. That only takes a few seconds -- not long enough to bother tower. The downside of delaying your check is that if you DO find a fouled plug, you have to taxi clear, do the de-fouling run, and then rejoin the queue for takeoff.