My S4 TII with S5 engine is having some real trouble idling. its boucing up and down and likes to stall out randomly. NO vacuum leaks at all i have been over it a thousand times. The thing is my a/f is always pinned on rich and i dont know what the wire colour is for the oxygen sensor from the factory. what colour is the S4's oxygen sensor wire? mine was hacked before i got the car, now its not hooked up

thanks
brandon

 

ECU pin 2D, gray wire.



If your gauge is pegged on rich it's most likely hooked up wrong.

 

thanks, that is a very usefull diagram! i am going to run my own wire to the ecu for the oxygen sensor of a thicker guage and run a ground strap to the oxygen sensor. Helped my turbo PGT and got me alot more (seemingly) accurate readings on my a/f guage (well as acurate as a narrowband can get)

the thing is the guage used to work fine untill a few days ago when the idle problems started to occure. it bounces up and down very badly....

 

no tachometer pick up on there????is that vref?

 

I keep meaning to add that. The trailing ignition timing signal is used for rpm: S4 is pin 1X; S5 is pin 1G. Vref is the 5V power source for the sensors.