Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Exhaust/ Emission

Hello all thanks for reading,

I am looking for some experienced opinions/ ideas for my scenario.

I have a 2008 Ford Focus with race headers, full stealth exhaust, and a high flow cat in place for my exhaust system.

For those who are familiar with the 2008-2011 models the stock headers came with two cats… I have replaced that header with a F2 race header (which is a CAT delete), and stock exhaust with the FSWerks stealth exhaust. The high flow cat I have installed sits at the mid point of the vehicle which is about 3ft from where the stock ones once were. I have both O2 sensors installed in their correct locations. (O2 wires are still stock, I had to extend the downstream O2 sensor to reach the new cat location). The CEL is on and the handheld reads:
HCM -> N/A
2AIR -> N/A
P0420CAT efficiency below threshold (Bank 1)

My inspection is due and I need to get everything ready to pass a NYS inspection. So here comes the question; What can I do that would get the O2 sensors to get the proper readings to pass the inspection? Or are there any other solutions out there that I am not seeing? Would a simple non-fouler on the rear O2 sensor work? Can a tune reconfiguring the emissions standards work? Im at a dead end folks and I could use some help. Thanks for reading.

You’re using a catalytic converter that isn’t working as effectively as the original. I know of know way to successfully fool the ECU into thinking it is. No special tuning will work.

I hope you kept your old parts. You’re gonna need 'em.

I suspect your “high flow” converter is more like a sham converter…It can’t duplicate the performance of the two CAT system it replaced…The only realistic option you have is to put everything back to stock on emissions test day…Lot’s of “tuners” go through this ritual…

Offhand, I don’t see an easy way around this either so I’m in agreement with mountainbike.