2010 Ram 1500 4.7 throwing P0420

[metalchewy]

So, I bought my Ram about a month ago. Higher miles (188k). I have put about 3 tanks of regular 1 tank-91 and 2 tanks -87 octane tanks thru it to get a feel for mileage. The day after I bought it I drove it home about 450 miles or so. No codes thrown at all.

Being a flex fuel 4.7 I wanted to try to get a feel as to how bad the mileage would be with E85. To see when it might make sense to run it and be cost effective. My truck uses about 1/3rd more fuel than regular gas. E85 won't ever be cost effective with its current price. 20% less than 87 octane. It did, however, give it more power as expected.

Now, 2/3 thru the tank of E85 It is throwing a P0420 on Bank 1. I cleared it, drove it 100 more miles and threw the code again.

My plan is to add 12 gallons 91 unleaded again and add some BG44K to try to clean things out.

If fuel system cleaner doesn't fix it, what are the next steps to go through. I've seen some conflicting info that it may be O2 related, or Spark Plug /wires/coils or that it is usually just the cat.

Any thoughts or ideas that might help??

 

[GTyankee]

P0420 Engine Code | Catalyst System Efficiency Below Threshold (Bank 1) - FIXD

P0420: Catalyst System Efficiency Below Threshold/Bank 1 is usually due to a defective catalytic converter, but other components can also be involved.

www.fixdapp.com

 

[Mister Luck]

We all find ourselves at the hand of fate and not that you should take this personally but for entertainment sake of other fellow members we all have or wished we had done something different in hindsight of our predicaments.

Prior to marriage of your acquisition.
I’m assuming you had already inspected the vehicle and changed all fluids that you did not personally know the history of.

At the least inspect and if questionable test
Wear components like
The radiator thermostat
Spark plugs
serpentine belt
battery
alternator

Pressure test the cooling system and test the coolant.

These could give you a baseline condition.

Now the best you hope for is to plead insanity and do the following

Compression test to find the weakest cylinder inspect the spark plug, inspect and clean it’s injector
Pull the O2 an inspect it for damage or cleanliness.

If by your good intentions you loosened up debris in the fuel tank and shot it through the injection system you may have a poor spray pattern or an injector can leak after shut down and wash the cylinder and pollute your crank case.

The other injector scenario is where the pattern is clogged and leaning out the combustion process causing excessive heat damaging the sparkplug electrode.

Either of the above can loosen coked carbon deposits in their combustion chambers and blow solid debris through the exhaust manifold to clog or pollute the cats and or sensors.

Intake air leaks or faulty sensors?
Exhaust manifold leaks can mess with O2 readings but
I’m not well versed in 4.7 idiosyncrasies.

Reading codes is kind of a game and inspection and testing way cheaper and more concise than throwing parts.

That is if you want to know your vehicle or if you want someone else to know her for you.

 

[metalchewy]

We all find ourselves at the hand of fate and not that you should take this personally but for entertainment sake of other fellow members we all have or wished we had done something different in hindsight of our predicaments.

Prior to marriage of your acquisition.
I’m assuming you had already inspected the vehicle and changed all fluids that you did not personally know the history of.

At the least inspect and if questionable test
Wear components like
The radiator thermostat
Spark plugs
serpentine belt
battery
alternator

Pressure test the cooling system and test the coolant.

These could give you a baseline condition.

Yes, I Inspected quite a few items before I bought it.
Radiator fluid - New. No discolored residue inside.
Spark plugs - New. Pulled a couple on each side.
Engine oil, clean with no burnt smell. Changed anyway
Air cleaner replaced.
Intake looks like it has never been removed, have strong doubts there could be a leak there.
Trans fluid, clean, non burnt, planning to change the filter soon.
Belt, New, No cracks.
Battery, 12 months old, water levels checked.
Alternator is working fine.
Cv boot on front right needs replacing.
UJounts, all good
Differential and Xfer case oil is on the list to change.

Based on your response, It sounds like you are recommending to pull and inspect all of the plugs for discoloration and run a compression test.

And to pull and inspect the 4 O2 sensors.

Thanks for the response, I appreciate it.

 

[metalchewy]

Ended up running the BG44K and 12 gallons of fuel through it today. Proceeded to run it all through, Some highway, some offroad. About 75 miles in, the engine light went off and the codes all cleared. No DTCs are found.

I figure whatever carbon the ethanol may have loosened up dissolved and blew thru while we were out.