Hello
I just got a 07 Explorer Ltd 4.6l 3v with 127k miles that had bad missing and manifold exhaust leak when I got it. It sounded horrible and drove just as bad. I replaced 3 coils and all 8 plugs so miss is gone and after driving about 40 miles more the P0420 code came up (only misfiring codes for about first 200 miles). I reset the CEL and it came back on again. Since the exhaust leak seems to seal itself up after 20-30 sec (don't hear the ticking) should I replace the upstream 02 sensors or all 4 sensors first? I am asking because I was going to get the Walker catalytic convertors for about $290 but local mech said start with the 02 sensors.

The truck only has 127K miles but was thinking maybe previous owner damaged the convertor driving with the bad plugs and coils with a rich fuel setting.

Thanks

 

Is it an 06 or 07? You said both?

 

Sorry it is a 2007. Turns out FordTechMakuloco of YouTube fame is nearby so dropped it off with him to diagnose. Sometimes its better to leave it to the pros instead of wasting time and money throwing parts. I will update as I find the answer.

 

I bought the same vehicle 2006 4.6 xlt black with leather with 90k last fall to fix and drive for a awhile. Parallel issues. I had to pull the heads to get to the stud bolts. 6 were broken. For $300 I took them to an expert. There was a rotted brake line. I used the emergency brake to get on the trailer.
I pulled the AC compressor as well and replaced. Found a nice set of wheels and tires from an Eddie Bauer.
I get a 430 after about 1500 miles of driving. Idles smooth for a about 15-20 seconds then goes rough.

My Autel Maxicheck says my sensors are passing voltage requirements.

However the catalyst monitor test fails Bank 2, rear to front, test voltage 7.62, max is 7.58.

I m shopping for a shop this morning.

The brakes have never bled very well. My Maxicheck runs the solenoids, but still not seeing any air.

 

Sorry never updated:
The shop ended up replacing both manifolds (Dorman), stainless steel studs/nuts, both catalytic convertors and rear exhaust (Walker) and everything was fixed. I ended up selling it to a friend whose boyfriend totaled in a few weeks lol