does any one know what the code p172 on an OBDII is caused by I know its system too rich, but what can cause it to be rich, I have a stock integra LS with a t3 turbo, 12:1 FMU, I checked the plugs and they look good, the engine sounds good when outside of the car but it sounds bad when inside, and I can't locate it could it be the cat or o2 sensors? any ideas?

 

are you loosing the missing link with your setup?

 

oh yes I am using the missing link

 

This code is set when the Long Term or Short Term Fuel Trim has reached its max or min value of +/-20%. The ECU arrives at these values based on O2 sensor feedback.

Extreme a/f ratios, aged sensor, or faulty wiring can cause this code.

With an FMU setup, I'd think your running pretty damn rich. Your O2 sensor could have been good but running so rich has fouled it out. Replacing the O2 will only lead you back to this scenario as you haven't corrected the cause for the problem.