Replacing front cats on '05 Escape 3.0V6

Hi all,

My daughters car popped up a P0430 when returning form a trip this week. I just connected my cheap scan tool and after reading the DTC I graphed the O2 sensors on the upstream cats. The image is attached. I first thought it seems odd that the B2S2 would follow B2S1 so closely, then I pulled up the B1 sensors and saw that B1S2 responded differently which made more sense. Checking my handy dandy ScannerDanner manual and looked at chapter 4&5 and confirmed that the downstream O2 should indeed respond much differently (closer to how B1S2 is behaving).

So, I think I have properly diagnosed the problem. It occurred to me that in addition to the cats and exhaust gaskets I would need an intake gasket set (at least the upper one) as the intake will have to be pulled to get access to the back manifold/cat. Is there anything else I'm not thinking of that I will need to complete the job? I'm pondering the wisdom of replacing all the O2 sensors at the same time. The engine has about 150,000 miles on it but they seem to be responding as I would expect. I seem to recall though that an O2 sensor has a limited life after which they are not as accurate?

Thanks for any advice!

It looks to me that both upstream O2 sensors are working okay B1S1 also looks okay but I want to test B1S2 by driving it rich and lean by either the propane oxygen storage test or by simply fluttering the throttle but you may damage them getting them out. The bad news is I think you need likely both cats, the downstream O2 sensors should be either fairly rich or lean rarely in between.

Link to Premium Video Cat testing

Thanks Andy. B1S2 did calm down once the cat warmed up a bit more but as both cats have the same mileage on them, i.e. a lot, I will replace them as a set and be done with it. They are expensive little buggers though...

Before you dig in too deep, maybe eyeball the manifold nuts to make sure none of the studs have snapped off. It's not as common on these as the 5.4's, but still happens. Mostly don't want you to get the manifolds off and not be prepared to drill/extract as needed.

If you're pulling the intake, consider doing plugs/coils while you're there? Getting the intake off isn't hard, but it might be nice to do some preventative stuff while you're there, if you haven't replaced those already.

The front cat is pretty dang easy, but the back one can be a real drag. 4WD doesn't help, if this Escape has it.