The Stang throws some codes...

[joshjwc9]

I have had a BBK OR X pipe on for about a week and the CEL turned on yesterday, I went to Autozone and they pulled the codes:

P0420 Catalyst Efficiency Below Threshold in Bank 1
and
Pending P0174 System too lean Bank 2

And I now have a leak on the drivers side, it isnt huge but can be heard at idle as well.

Couple Questions:

Which of these is because of no cats or are they from the leak on the manifold to the midpipe?
Could an exhaust leak cause the car to almost stall at idle and then catch itself and go back to normal, or is it the IAC? (It only does it when Im stopping at lights, not when I first start it at all.)

Thanks for any help :SNSign:

 

[screamin gt]

may not be much help, but the guy I bought mine from said that after he put the exhaust on it caused the o2 sensors to trip, so he had to install o2 sensor by-passes.

as far as your stalling rough idle problem, having the 02 sensors tripped (by the new exhaust letting too much fumes pass them) tells your computer the engine is not running right so the computer tries to correct the problem by altering the fuel mixture, which makes it run rough, since it is trying to fix a problem that doesn't really exist in the first place.

if that doesn't make sense to you thats fine since I just pulled all that out my my a**.

 

[joshheat25]

As for the P0174 I also am throwing that code I am going to replace my O2 sensors and hope it clears up. I also have a rough idle and it will almost die at lights. I already changed my IAC. I'll let you know.