running lean
 

I'm running a catless header and I've been throwing a code p2096, post catalyst fuel trim system too lean bank 1. Any idea of risks for this? I know if its too lean I can blow my motor so I don't want any smart ass answers. I'm looking for actual technical discussion as to what is actually too lean and I will provide logs of Afr commanded and measured with corresponding rpm. Is there anything else I should be logging like load or anything else?

Did you run any sort of oxygen sensor spacer? I ran into this code too. So I took the spacer out and got po420 code. Long story short: watch your fuel trims. As long as you are +/- 5% from 0 you are fine. However CEL will affect you traction control systems. So spending time with spacers and washers to get the perfect spot in between where you will get lean code from being too far out, or p0420 code from being too close I've got over 7k on my Catless header with no ill effects and fuel trims +\- 5%

I have this weird 90% thing on my downstream sensor that was given to me when I bought the exhaust.

Basic question, is the car tuned for no cats?

No tune.

ECU is not getting an expected rear o2 sensor reading because of the catless header.

The rear o2 sensor is used for the catalyst monitor (which most people are aware of) but it's also used to adjust the reading of the front o2 sensor in cruise operation. It accounts for degradation in the front o2 sensor.

Which sensor is bank 1 and which is bank 2? If bank 1 is the downstream that explains everything, if bank 1 is the sensor before the cat I'll have some questions. The obvious answer is to have the car tuned, but I have other things that thousand dollars needs to go to, on the other hand if it is running too lean it might be worth it to do a tune first.

We only have bank 1. Sensor 1 is up stream aka primary O2 aka front sensor aka pre cat. Sensor 2 is downstream aka secondary O2 aka rear sensor aka post cat.

The lean code probably indicates sensor 2 is a bit too far from the stream of exhaust gas or has too small of an opening.

It was too far. I removed the spacer, probably gonna get a running rich code. Thanks for the help.

or cat inefficiency code P0420. Vibrant sells one you can tweak, it has 3 different orifice inserts IIRC.

How long were you running the spacer before the code first came up? I've been running an angled o2 sensor on my Borla UEL header for 2,000km now. 2 track days and a lot of highway running with the cruise control on, no CEL so far.

It comes on pretty quick. Could you post a pic of how yours is mounted please?

Here you go

http://i374.photobucket.com/albums/o...ps8a13de1e.jpg

http://i374.photobucket.com/albums/o...ps1036cdda.jpg

That helps, but do you have a close up so I can determine the angle in relation to the exhaust flow?

you spaced the 2nd sensor and not the first one? i didnt know if the 2nd one can throw lean codes because its the first sensor that checks a/f. i used 2 sparkplug spacers. one drilled. no codes in weeks

Spaced the second(down stream) sensor. Threw a lean code, pulled spacer and got an inefficient catalyst code.

Just get a catted front pipe with an O2 bung after the cat and move the secondary O2 sensor there.

In case you haven't already discovered this or blown your engine, never under any circumstances whatsoever install a spacer of any kind on the primary O2 (AFR) sensor. Adding a spacer to this sensor will cause your engine to run lean. Depending on the spacer effect, possibly dangerously lean. Remove it ASAP.

The secondary O2 sensor (narrowband) monitors catalyst efficiency from it's position downstream of the primary cat and is the only sensor responsible for setting the typical P0420 catalyst efficiency CEL when the primary cat is removed. The spacer goes on this sensor only and the effect is to cause the sensor to read less oxygen which it sees as a properly functioning catalyst.

i know thats what i said, to space the secondary o2. lol On this car a p0420 can be accompanied by a lean code as well. i told him not be sure not to space the first one.. but im running o2 bypass on openflash now. the spacer dont work long

I have a tune. No issues anymore.

Sorry 'bout the misunderstanding. My bad.


Cool. FWIW, I'm running a Borla UEL, a mini-cat spacer on my secondary O2 and a Visconti stage 2 tune. Mostly CEL free but I just had a P2096 for post-cat too lean.

I'd get away from a Visconti tune if I were you.

Why?

I have no information from personal experience, but I've seen the power his tunes put down, and I've heard from people who have delt with him and in my opinion he is not as good of a tuner as he is made out to be. He is rude, negligent and he has been charging his flex fuel customers for an upgrade that should be included in the kit to prevent fuel from leaking. I have no Ill intentions towards him, I wish him success, but I would not do business with someone like him nor would I recommend anyone else do so either.

I've heard all the same viral BS on this forum spread by a handful of Visconti haters but have never been one to follow the mob mentality or care what or who is popular with them at the moment.

I've never met John Visconti or even spoken to him as my tune was done through a 3rd party shop. All I know is that he remotely dyno tuned my car, added 17whp and his tune has been without flaw.

I hear that Beethoven was a bit of a prick too but I still appreciate his music.

If you like his work, then that's all that matters for you. Cheers