My second set of sensors have gone bad. What could be causing this? I have a k&n filter and a 19% pulley with a home brew header. My code reader says o2 bank 1 sensor 2 is suck lean. My car won't allow me to go to full throttle and is VERY slow now. I have 20k miles since the Pulley swap. Ohh, and i have MM MIL eliminator (Just a stupid diode that cost $60 ). Suggestions?

 

Do you have upgraded engine software?

The techs at MINI of Peabody told me of a few killed catalytic converters and the common theme was upgraded pulley/etc with no engine software - I guess the original software is just so confused by the upgrades that it can't properly run the engine and exhaust gases suffer.

 

Autoxguy305,

What are the actual "P" code numbers? Have you checked your catalytic converter for excessive back pressure? Got similar codes and no power above 4000 RPM with a 19% pulley. Found 7 PSI back pressure at 2500 RPM measured at the pre-cat bung. A new cat is on order.

Let us know what you come up with.

Regards,
John Petrich in Seattle

 

Codes of this nature often indicate an inability of the ECU to adjust for the lean condition and so the software assumes it is the O2 sensor that is bad. I have seen many cases where the problem really was a vacuum leak, allowing un-metered air into the intake. Might be a good place to start looking.

 

OK I am on shakey ground here but I solved the problem with a "catch can". Depending which sensor they can get "gunked" with oil.....I saw this when we pulled them out of my car. Get your ECU updated for your mods (MTH, UNichip, GIAC et al) and as Pete said have someone go through the car and make sure all fittings, hoses etc are in tact.

 

Since your "MM MIL eliminator" is the thing plugged in where your rear O2 sensor should be, why don't you try removing it?

 

who did the development of the "home brew header?" I would look there as well.

 

I have no cat so backpresure isn't the problem. I pulled the intercooler today and it was ALL junked up with oil. I'm making a catchcan tonight. I'm going to install a wideband to see what the car is doing, then i'm going to looking into either programing, or a standalone setup.

Anybody have any experience with standalone EMSs on the mini? I have an 84 jetta with a 1.8t in it running on emerald EM. Whats out there for our cars?

 

I'm glad that helped.....it's amazing how much a catch can helps keep it clean in there