billyjo

ok this is a common problem due to brenspeed turns off these monitors so they can give you the power and fuel the car needs. its easy to do which is go back to stock and drive about 30 to 50 miles being easy on the throttle not to floor it and lean out the mix due to your cai. should have the monitors go back to running, get it inspected and then go to the next parking lot and put the tune back in. you will relize how crappy the stock setting is and if you take it easy on the throttle you wont hurt anything. i did this excact thing and passed in mass which is the second worst state CA being the worse,

Audioi

I went to have mine done 3 times before I called Brent @ Brenspeed to find that the o2 sensors were off.
Easiest to set it back to stock, do the reset drive and your gold. Its a PIA and I will make sure it wont happen again to me.

A_J

Brenspeed willsendyou a emissions friendly tune if you email them - I haven't run mine through testing yet, but in theoryyou should be fine just uploading that tune, and driving it for a while..

jmanpatsfan

What are O2 sensores for? Is it harmful in any way that they are turned off?

illin

O2 sensors examine the post combustion fuel/air ratio and then have the car adjust the air/fuel ratio according to what Ford determines as "optimal". Most race tunes are going to run richer than what the EPA would allow...thus them being called "race tunes".

Running a hair rich is certainly not going to hurt anything. Running lean is certainly not good though.

billyjo

o2 sensors are the only real time readings the computer has that tells it if the car is running rich or lean, it is attached to the computer in the form of two programs, short term fuel trim stft and long term fuel trim ltft. when the car is running lean their is more o2 in the exhaust so the stft will tell the computer to give more gas. stft is a quick fix happens with in milliseconds but if it needs it all the time the stft tells the ltft tokeep it a constant and it goise up a number. LTFT has 25 numbers at around +19 your check engine light will go on due your car is running to lean and it has a problem and if its - 19 same applies but it means it to rich. so the o2 are a big part of how your car runs. when you turn them off the adaptive strategy relies on the program and doesnt adjust as much and if you remember a rich gas at around 12 to 1 is the best but the car is programed to have it at 14.7 to 1 so when you turn them off it lets you keep the mix rich. I hope that explains, that is a short explanation but if you have any questions please ask

MrSandman

How big is the performance loss when turning them on? Brenspeed just emailed me an updated tune for my 3.73 gears (i have an automatic).. and I asked him to make sure it was "emissions friendly". I just loaded the tune.. but have not been able to drive the car yet today to see what difference the shift schedule adjustments made.

howarmat

There is no HP different, the rear O2s are just for emissions only

I wouldnt take the tune out and and drive with the CAI though....bad advice unless its only a couple of miles or something. You will throw a CEL then and they will fail you for that! You are just going to have to wait until you can get the updated tunes. DO NOT drive with the C&L and no tune especially for 30-50 miles

dan_h

sounds like a plan...I'll contact Brenspeed on Monday!

blk05stang

Anyone know if B A M A Chips disables the rear O2's in their race tune?