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Hello - I have a 2005 honda pilot with 235k miles in need of a timing belt. We needed another car anyway so picked up a 2008 pilot with 175k miles in really nice shape (no rust, which is hard to find in MN) so I could take my time with the 05. We test drove it for 150 miles, I checked it for codes and thought I looked it over pretty good. Runs and drives great. Pretty much better in every way than the 05.

The Honda dealer replaced timing belt, tires, front and rear brake pads and rotors before we bought it.

We drove home about 50 miles after picking it up with no issues. The next day, check engine light with P0420. After researching the forum, it seems like the first thing to do was to do a valve adjustment since I have no idea if they have ever been done and check/replace the spark plugs.

The intake looked like this inside. I'm going to assume this isn't normal.

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Also, bank 2 (4-5-6) are darker in color and not as clean as bank 1.

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Most of the intake valves were loose. Exhaust valves on 1-2-3 were a little tight. Most were .008 and a few .010 and .011.
Exhaust valves on 4 and 6 were too tight for .008, but still had at least some gap. 5 had no gap at all on either valve.

I have adjusted the valves and cleaned everything up as best I could and re-assembled with new spark plugs.

Is there anything else I should do before taking it for a drive tomorrow? If it runs good still, is there anything else I should look at doing? If the cat code comes back, I'll continue to look into that of course.

Thanks for any input!
 

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Since you have the intake off, make sure the EGR passages/equivalent are cleaned. As for the discoloration, my thought is it is heat related. E.g. you actually have an issue with one of the Catalytic converters (P0420 is Bank 1, e.g. closest to the firewall). A high quality synthetic oil (with a good detergent package) should clean that right up after a couple oil changes (provided you address the catalytic converter). Since you mention your in MN, a bolt up replacement from a reputable brand shouldn't be more than $150 (E.g. Pacesetter has one for $137 via Summit Racing - though shop around).
 

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Adjusting the valves won’t change the code. You need a new cat. My engine had the same discoloration but also had a cat code.
 

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check engine light with P0420
There are two kinds of people in the world: those who successfully clean their catalytic converters with a gallon (not just a quart) of lacquer thinner, and those who fail to do so using only a quart (not a full gallon), per tankful and driving all the tank down.

Which one are you?

Let the friendly debate ensue.
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That valve train discoloration is normal, it's due to the PCV system. Bank1 gets clean air from the TB tube and Bank2 gets air from crank case mixed with gas and oil etc. Just make sure PCV is working properly and that the passages on Bank2 valve covers aren't plugged up.

The black debris on the intake plenum looks like carbon deposits, mostly likely carbon build from EGR system that made its way into the plenum.
 

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That valve train discoloration is normal, it's due to the PCV system.
Agree. Mine was identical when did the valves a few months ago. Clean / replace the valves and passages in the cover. I ran SeaFoam through mine after I put it back together for good measure. My highway mileage is consistently up about 1.5 mpg.
 

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Discussion Starter #7
That valve train discoloration is normal, it's due to the PCV system. Bank1 gets clean air from the TB tube and Bank2 gets air from crank case mixed with gas and oil etc. Just make sure PCV is working properly and that the passages on Bank2 valve covers aren't plugged up.

The black debris on the intake plenum looks like carbon deposits, mostly likely carbon build from EGR system that made its way into the plenum.
I'm glad to hear that how it looks is normal.
I've already got the valves covers back on. What needs to be cleaned on them? I cleaned everything I could see in the intake. I really don't want to pull the 08 all back apart unless it's really needed. I did order a new pvc valve for each pilot so I'll put those in. It appears the EGR valve on the 2008 has been replaced recently before I bought it. It looks brand new with no dirt at all on it.

Took it out for a 30 mile drive today and everything seems good. It didn't set a code for the Bank 1 cat yet, but I was watching the chart and the bank 1 didn't seem right based on the 1 video I watched on what to look for. It is definitely more jumpy than bank 2.
 

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Discussion Starter #8
There are two kinds of people in the world: those who successfully clean their catalytic converters with a gallon (not just a quart) of lacquer thinner, and those who fail to do so using only a quart (not a full gallon), per tankful and driving all the tank down.
Anyone ever tried this on a pilot? I'd hate to do damage to the fuel system with a chemical it wasn't designed for. I may try cleaning the cat and putting it back on before actually replacing it (depending on how hard it is to put in.

Will it hurt anything driving it with the bad cat? From what I've found, it sounds like no unless it actually starts plugging up.
 

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Anyone ever tried this on a pilot? I'd hate to do damage to the fuel system with a chemical it wasn't designed for. I may try cleaning the cat and putting it back on before actually replacing it (depending on how hard it is to put in.
If it's not rusted on from road salt or practically welded on because of extreme heat, that might be a preferable solution in most cases, for folks for whom it looks like it's coming off easy,

However, I don't think the lacquer thinner solution would harm anything since it's petroleum based. But YMMV, literally. :)


Will it hurt anything driving it with the bad cat? From what I've found, it sounds like no unless it actually starts plugging up.
I would say no, so long as they're not too far gone from the 5% off when they start throwing the code.
 

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Will it hurt anything driving it with the bad cat? From what I've found, it sounds like no unless it actually starts plugging up.
I'm confused....isn't a clogged CAT a bad CAT and a bad CAT a clogged CAT?
 

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I'm glad to hear that how it looks is normal.
I've already got the valves covers back on. What needs to be cleaned on them? I cleaned everything I could see in the intake. I really don't want to pull the 08 all back apart unless it's really needed. I did order a new pvc valve for each pilot so I'll put those in. It appears the EGR valve on the 2008 has been replaced recently before I bought it. It looks brand new with no dirt at all on it.

Took it out for a 30 mile drive today and everything seems good. It didn't set a code for the Bank 1 cat yet, but I was watching the chart and the bank 1 didn't seem right based on the 1 video I watched on what to look for. It is definitely more jumpy than bank 2.
The valve cover passage can sometimes get clogged, not too common though. I wouldn't worry about it too much, my 07 with 230k barely need any cleaning I only did cause it made me feel better. I'd just leave it till you need to go under the valve cover again, or when it start leaking through the valve cover gasket.

As for the EGR, it may be new but there's probably build up on the ports. There's guide for cleaning it on youtube.
 

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I'm confused....isn't a clogged CAT a bad CAT and a bad CAT a clogged CAT?
Not necessarily. The honeycomb material in the Catalytic Converter can always disintegrate. The biggest killer of them is running rich / unburnt fuel (which there can be a plethora of causes for). If the code comes back for the Op, would advise they check their local emission requirements, and if required replace it with one from Pacesetter or the likes. If not, feel free to gut it if it's already bad or consider replacing both banks with test pipes (though this will likely increase exhaust noise, so not for everyone).

EDIT: One other thing to try/consider is the "Italian Tune-Up". These J35's feel like a caged lion compared to the 4 cylinder's I've driven in the past. Got to open the cage, and let them EAT from time to time... RAWR!
 

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EDIT: One other thing to try/consider is the "Italian Tune-Up". These J35's feel like a caged lion compared to the 4 cylinder's I've driven in the past. Got to open the cage, and let them EAT from time to time... RAWR!

... and then vote in the poll. :)

 
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