- posted 5 months ago
every 60,000 km ; *'s resistance betw the 2 pins connected to yellow+white & red+black wires ( on *'s plug ) ? with wear ( as the electrical c ontact areas ?, the ampere flowing through ?, so resistance ? ). A usable * ( @ rest ) can have just 411 ohm but a worn * ( ca using idle rpm to fluctuate betw 1400 & 600 ) can have 1110 ohm. ECU interp rets this higher resistance as throttle plate having turned >20º, & so injects more petrol, so (i) spark plugs foul (ii) bottom of the idle air s crew ( on throttle body ) gets much soot, so less & less air can flow past, so idle rpm keeps dropping. Meters' panel does not show, & very few users connect a volt meter to, O2 s ensor's output voltage ( -ve during idling, if sensor is not hot enough ), so nearly no user can notice too much petrol is injected.