I think I found the cause of my recurring P0420 code

[MyExplorer03v8Lim]

I've been chasing the P0420 code forever. Convinced I need to find the source before I swap the cats. Well boys, I think I may have found it.

A little back story, the code only seems to pop after I've been giving her wide open throttle for 5-10 seconds. Seems to be related to heat or stress.

I was worried I'd been dripping coolant into the combustion chambers from an internal intake gasket blowout. Maybe not.

After much looking around I embarrassingly finally found a pretty glaring issue. There's a snapped stud on the low side of port 4 @ the exhaust manifold (right hand side, back of engine). Also, the flange where it bolts to the cat is snapped on the manifold side.

You can see pics here:

http://imgur.com/aRf65jI - broken flange @ cat pipe. Broken on manifold side.

http://imgur.com/070U2z2 - broken stud @ cylinder 4.

So my question to you guys is what should I expect to pay for a shop to do this job. And follow up question, should I try to do it myself. And if I'm doing one, should I do both?

 

[lincolnshibuya]

is it noisy/loud on cold start up or acceleration?

 

[shucker1]

So my question to you guys is what should I expect to pay for a shop to do this job. And follow up question, should I try to do it myself. And if I'm doing one, should I do both?

Key question here is what is your experience level and comfort level of doing major work.

I would not even try that exhaust stud unless the head were off the engine. Too much of a PITA and too many chances to screw up with it on the engine.

So if I had one off, I would jerk the other one and get them both reworked while they are off. Just because..

Others will disagree but he have "Bigger Grapenuts" than I have.

 

[MyExplorer03v8Lim]

Key question here is what is your experience level and comfort level of doing major work.

I would not even try that exhaust stud unless the head were off the engine. Too much of a PITA and too many chances to screw up with it on the engine.

So if I had one off, I would jerk the other one and get them both reworked while they are off. Just because..

Others will disagree but he have "Bigger Grapenuts" than I have.

Popping off the heads takes some serious grapenuts in my book. But I like where your head's at dude.

You're definitely right. And itd be a hell of a good opportunity to see what the internals look like too.

Maybe I have a winter project on my hands.

Now in your oppinion, is it better to pull the whole engine, or to pull off the heads. Call me crazy but it almost seems "easier" to get the entire engine out. Thoughts?

 

[MyExplorer03v8Lim]

is it noisy/loud on cold start up or acceleration?

Not really to be honest. But sometimes on a cold start it has a rough idle. Also, sometimes the accelleration feels a little delayed. Like I'll step on the gas and get nothing for a second and then it pulls.

 

[shucker1]

Now in your oppinion, is it better to pull the whole engine, or to pull off the heads. Call me crazy but it almost seems "easier" to get the entire engine out. Thoughts?

I honestly can't say because I own a 98 and I'm very comfortable with the work required. Not to sound pretentious but I've been wrenching on cars for quite a while so I would do my research and just dive in, more than likely smacking my head on the bottom in the process, but it happens.

LOL.

I would defer that question to folks like @Turdle, @CDW6212R or others who have vastly more knowledge than I on the Explorer series.

 

[Drewmcg]

Pulling the 4.0 is no picnic--I imagine that pulling a 4.6 would not be any easier. Unless you have another reason to pull the engine, I'd say avoid doing so if you can.

 

[MyExplorer03v8Lim]

Pulling the 4.0 is no picnic--I imagine that pulling a 4.6 would not be any easier. Unless you have another reason to pull the engine, I'd say avoid doing so if you can.

Only other reason to pull the engine would be to satisfy my obsessive need to clean and check everything on my vehicle to make sure it's ship-shape

 

[Drewmcg]

Yeah--not a good enough reason, IMHO! You'lll indulge your obsessiveness just plenty pulling the heads....

 

[MyExplorer03v8Lim]

Yeah--not a good enough reason, IMHO! You'lll indulge your obsessiveness just plenty pulling the heads....

Ha! I'm sure you're right!

 

[shucker1]

Just a little back story here.

I had a bad valve on my 5.0L. Pulling both heads wound up turning into a camshaft, roller rockers and pulling the engine to change the oil pan and rear main seal.

Things were great till I roasted the #1 piston.... (It ran too good). LOL.

Now it's back out again and the engine is complete on a stand as a 331 stroker while the rest of the project waits of monetary funds.

I got a bad case of the "This should Be Cool" fever.

It's a 3rd car so time is not of the essence.

If it's your primary transportation stay within your set project limits.

 

[MyExplorer03v8Lim]

Just a little back story here.

I had a bad valve on my 5.0L. Pulling both heads wound up turning into a camshaft, roller rockers and pulling the engine to change the oil pan and rear main seal.

Things were great till I roasted the #1 piston.... (It ran too good). LOL.

Now it's back out again and the engine is complete on a stand as a 331 stroker while the rest of the project waits of monetary funds.

I got a bad case of the "This should Be Cool" fever.

It's a 3rd car so time is not of the essence.

If it's your primary transportation stay within your set project limits.

Sounds like a fun project! I'd be lying if I said I didn't have to google most of the stuff you're talking about... but it still gets me going! Good luck and enjoy!

 

[rocco123]

Have you looked at your fuel filler neck for the 420 code? You would have to remove it to see if it's rusted out. My 02 had a bad one a few years ago

 

[MyExplorer03v8Lim]

Have you looked at your fuel filler neck for the 420 code? You would have to remove it to see if it's rusted out. My 02 had a bad one a few years ago

Really?! And that set off a P0420 code?

 

[boominXplorer]

P0420 is for an unclean catalytic converter reading. Has nothing to do with gas tank vent. It's either a small leak between the cat and the engine or the cat is going bad. Honestly if you can't hear the exhaust "tick" on a cold startup from that broken bolt area then it might actually be a bad cat.

 

[MyExplorer03v8Lim]

P0420 is for an unclean catalytic converter reading. Has nothing to do with gas tank vent. It's either a small leak between the cat and the engine or the cat is going bad. Honestly if you can't hear the exhaust "tick" on a cold startup from that broken bolt area then it might actually be a bad cat.

Thank you. Thought I was taking crazy pills. I knew P0420 could have a few potential causes, but evap leak didn't seem like one of them

But dammit now I can't go without checking my filler tube! Must replace all the worn parts!

 

[MyExplorer03v8Lim]

So, with a second set of ears and eyes on the thing, it turns out I don't have an exhaust leak coming from the manifolds, which buys me a little time before I do that job.

But here's another question: my mechanic advises me that all catalytic converters except OEM or C.A.R.B. compliant ones are total crap.

I only need the passenger side, and the one from Ford is like $2k. So where do I get a non-crap right side cat?

 

[Drewmcg]

I had a muffler shop in austin splice (weld) one in for something like $380. they also replaced third cat with straight pipe for another$150 b/c material from upstream cat had clogged it.

check rockauto.com