Finally got the truck back after a month and a half (and $10k later...) with a new used engine after the PCV failed and probably took out the entire engine.

The shop warned me the check engine light might come on if the catalytic converters were damaged by the old engine burning oil. Sure enough, second trip after picking it up it came on. Code P0420 (Catalyst System Efficiency Below Threshold (Bank 1)). Also noticed the exhaust smells of burning oil and saw some faint oil smoke at idle.

Assuming the catalytic converter(s) are damaged, what are the alternatives to buying brand new cats from LR ($$$$)? Can I get universal weld-in ones like Magnaflow? The diagram makes them look like they have a bend in the cat itself which seems odd and like aftermarket might be tricky to fit.

Is there any chance the oil just have to burn off and I'll be good to go?

 

I chased the P0420 code for some time.based upon advice here i replaced the airfilter with a K&N, cleaned the MAS, replaced the PCV valve, and cleaned the thottle body. (a lot of oil was seen in the intake manifold) the code did not go away with any of these fixes. I put a bottle of mr gasket cataytic converter cleaner in the tank stuck with premium fuel and the light goes out on its own after a few minutes of driving.

I do wonder how a bad pcv valve ruined the engine?

 

When I got home, I took the temperature of the exhaust pipes right before and right after the catalytic converters, figuring if they were shot or not working well, there wouldn't be much of a difference before to after.

Before the cats was about even on both sides at 300F, and right after the cats was also fairly even 420F one side, 400F the other.

At least something is happening in there still! There may be hope yet.

Not entirely sure as it died when it was with the mechanic. Top theories are that the engine had some preexisting damage from low oil and the stress of burning all that oil was the final straw, or that it burned so much oil that it went low and caused damage enough to throw a connecting rod.

 

I forgot, in the mix was two new O2 sensors. If you do an internet search you will find that there are nearly 200 causes for that code. Even with all of the new parts I put in and after I verified the long term and short term fuel trends were within limits, my last choice is a new converter.
Like you, I may be burning oil in the right bank and hate to throw a $600+ converter on it just to clogg it up with oil. Especially since the cleaner seems to be working for 3 or more months at a time now.

Good luck. Let us know how it turns out.

Jeff

 

So should I try the Mr. Gasket Cataclean then? Seems like it at least worked a little bit for you. O2 sensors are on the list if driving and additives (maybe) don't work.

 

Maybe. It is a temporary fix. It does clean the cat. I get 2 to 4 months before I need the cleaner. Sooner or later I will need to address the oil comsumpion on the right bank. For you, if the oil burn is bad, it will be needed more often. A new cat will clog up in time just like the one you have now, but may take longer since it may be "cleaner" at the beginning.

It may not be oil burn, it may be too rich fuel because the O2 sensors are bad. Check short and long term fuel trim to see.

There are many basic mechanic web sites thst talk about the P0420 code. They will also show how to
read the fuel trends.

Try reading here it may help explain how it works.

https://www.discountconverter.com/ca...rter-&News=120

 

Thanks for the link, very helpful information. The truck isn't burning oil anymore. It was more of a one time (catastrophic) event.

My gas mileage has taken a hit since getting the truck back, I wonder if that could be related. I used to get 13-14mpg, right now it is sitting at 9mpg after about 160 miles. No rough running, misfires, etc. Plugs are new.

LTFT looks like 3.1% for Bank 1 -0.8% for Bank 2. Normal looking, right?

O2 sensor voltage (again, not sure which is which) is between .16V and .67V for one and .09V and .14V for the other. Again, pretty normal looking, unless I'm looking at the wrong O2 sensors.

 

In CA, you must use factory cats. Heard Magna flow cats are available but don't last as long as factory. Each factory cat is about $1k. Sometimes change one cat will cause the light to come on for the other cat. So, you may need both cats to get the light off, fyi.

You gas mileage maybe taking a hit if the cats are clogged, restricting air flow.

 

Even if I have to replace the Magnaflow cats every 15,000 miles, I'd still be saving money though.

I thought the same regarding the clogged cats, but checking the vacuum pressure it doesn't seem to be the case. Vacuum pressure is normal and reacts normally to throttle. I'm not getting any drive-ability issues either, like hesitation, stumbling, or rough idle. No symptoms of an engine struggling to breathe.

 

As I recall the order, cost wise would likely be:
Clean MAS
Clean Throttle Body
Change Air Filter
Change PCV Valve
Change engine oil
Change MAS
Clean Fuel Injectors (profeesional service not just a bottle of juice in the tank)
Change O2 sensors
Diagnose fuel trend issues
Diagnose possible vacum leak
Change conveter
Fix engine oil burning problem.

See, Easy fix! No seriously this can be one of those codes that is fixed quickly or challenges you for 6 months to a year looking for the cause.

Sort of like that darn TPMS intermitent messages about a tyre not being monitored every few months/ years

Keep us informed of the progress.