In article ,
says...
I get my 25 yr old oil & hot air furnace serviced every other year.


But he didn't do the ?CO2? test-- where a probe is placed in the
stack.

CO - Carbon Monoxide. Tests for a cracked or otherwise
defective plenum. Not a bad idea to have a CO detector in
the living space (unless your house is rather leaky) anyway.

Maybe
once every 10th [or 20th] cycle you can hear the furnace start-- then
stop-- then start - sometimes as many as 5-6 times. The next cycle
is always perfect. The blower fan works steady through this
stuttering so I've ruled out an open in the electrical feed.

Speculating here, but could it be the thermostat that's not
making a reliable contact?


Another random and discomforting problem is some exhaust smell on rare
occasions. I think I did catch this one once-- The burner fired &
though it sounded good, there was a lot of smoke & it was coming out
of an old probe hole in the stack-- and around the damper in the
chimney.

Partial flue blockage? Or maybe just an occasional down-
draft due to wind conditions.

--
Mark

The truth as I perceive it to be.
Your perception may be different.

Triple Z is spam control.