Based on OBD II Standard PIDs
PID(hex) 11 Throttle Position value from 0~100%
How could we use this data to predict if there is going to be a problem?
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By using OBD to get some key data, I developed a method to detect "throttle" related emission problems.
=== Background ===
The engine of the vehicle goes into the idle state (engine speed > 0, vehicle speed = 0) when waiting for the traffic lights. If the engine does not obtain enough air because of a throttle related problem (but not worse enough to flameout), then ECU will control to inject less fuel to maintain an Air/Fuel rate. The engine speed will drop (a small or big variation).
=== Method ===
=== About the Maths ===
S - engine speed
T - target idle RPM
e - variation tolerance of engine speed during the idle state
if | S - T | > e, then the idling engine speed is not stable
p - throttle position
t - time
R - the changing rate of the "throttle position"
R = ΔP/Δt
if | R_max - R_median | > e during a period of time,
then we could say that R is not stable, which means, he throttle is getting stuck somehow
=== Data collected from OBD ===
=== welcome to post your thinking ===