im attaching a log of my idle. my car has had a rock solid 14.7-14.8 afr at idle, and now suddenly after an o2 dump install my car is idling at 17-18.0 afr. at wot the afr seem to be fine. another thing to note is that we swapped the o2 sensor because the one in my old o2 housing was cross threaded. another weird thing is that usually when the afr goes all the way up to 18.0 the rpm will dip and want to stall, but now with it at 18.0 it feels the same as when its at 14.7. any input would be appreciated. thanks

 

leak at the o2 housing?

 

I agree with the leak theory.

 

yes I would say leak and the sensor is getting whiffs of fresh air.

 

what is the best way to find an exhaust leak

 

Pull off the o2 dump, apply a generous layer of orange gasket maker on the entire o2 dump flange + layer a fresh gasket on top, and retorque it back on; it's happening between the o2 and the turbine housing of your turbo.

 

Whats this orange gasket maker? I used copper gasket spray on the gasket I have on my car, but I don't think its the best option.

 

Just use a new factory gasket, not the crappy ones that come with the 02 housings. SHould not need any sealer with the factory gasket.

 

the dump comes with a copper sealant on it that acts as a gasket, if thats what you guys mean

 

yes copper is what it is.

 

You have an exhaust leak somewhere before the wideband sensor.

 

found some loose bolts on the manifold and one that was missing, tightened them up and it still idling lean.

i may be wrong, but when the car is at idle, doesnt the ecu read directly from the front o2. and if i was to get a bad o2, it could be causing the lean readings? just a thought

 

I agree, this was happening to me!

 

The stock gasket can't be used with an O2 dump as it doesn't completely separate the chambers.

Did you splice wires when you replaced the O2 sensor? I've heard that the signal wire can be quite touchy when it comes to splicing. If you did splice did you solder the connection?