So I am getting an intermittent check engine light that when the codes are read indicate efficiency issues with both catalytic converter banks.

No other codes thrown.

The truck runs flawlessly, no issues at all. I can't imagine that the cats are dead although it is possible I guess. It's not burning any oil that I can tell. In an effort to diagnose I started to walk the engine ventilation system and pulled the PCV out to check it.

I'm used to old schools PCVs where you can shake them and hear the check ball rattling around but there is nothing like that from what I can tell in the LR3 PCV. No rattle when shaken and it really doesn't look like there are any moving parts in there. Air will flow, unrestricted, through either end of the valve as I check it.

Is this normal?

 

Yes, Its normal. I have never dissected one, so not sure of the mystery behind its function.

seems to be no moving parts, air flow both ways.

 

Thanks abran.

It must act as some kind of centrifugal oil separator and allow any liquids to pass back into the valve train but allow the vapor to enter the intake.

The last oil change I swapped over to Mobil1 0W-40 since I had a couple of BMWs as well. I'm wondering if the low viscosity at startup might actually be causing oil to enter the intake and be screwing up the cats causing the efficiency errors. I'll probably do another oil change and go back to Castrol 5W-30 and see if that corrects it.

 

If you take off your throttle body you will be amazed at how much liquid oil is hanging out in the upper intake manifold.

 

If the cat codes were caused by a leak somewhere, I would guess you would have other codes. What codes are they specifically? For efficiency?

To your first point, yes the catalytic converters can go bad rather early from what I've heard. Usually there are some other circumstances that help them along. For me, my PCV clogged, filling the intake with oil. I replaced one of the cats, but still got codes so I replaced the O2 sensors and haven't had codes since. Don't know if the cat was actually bad or not, but start with the O2 sensors if you don't find a leak.

 

I'm assuming you are talking about the V8 engine? V6 owners: there is an electrically operated PCV valve on the driver side valve cover towards the fire wall. There is an actual valve or pellet in this PCV that can get gummed up causing rough idling and stumbling, etc. lol.. maybe Im the only LR3 owner here with the V6.

 

Is there any reason a PCV reroute can't be done to eliminate oil vapour from entering the intake system? Or is this something that is only done on diesels?

 

So as a follow up to this since it's been several weeks and previously this amount of time passing would have triggered the cat efficiency codes after I reset them.

No codes.

Solution? Got rid of the Mobil 1 0W40 and replaced with 5W30. It looks like the thin nature of that oil at colder temps was letting it get into the intake through the PCV (which is one odd piece of equipment in that there is no valve in it). I have to assume that either the burnt or unburnt oil that made its way through caused issues in the cats. I haven't seen the codes since the oil change.

So, even though Mobil recommends 0W40 for practically every European car/truck, I won't be putting it back in the LR3. And to the poster who asked: it is the V8.

Another poster asked about putting a catch can in and I have to say I thought about it. Technically a no-no since you'll be venting oil vapor into the atmosphere, but as a check to see if the issue is related to the PCV system, I think it would be a good test. Just block off the port in the intake manifold and all should be good for testing.

Thanks for the input everyone!

 

No your not and I love my V6.... Interesting I thought lately when I was idling for a long time I thought every now and again the engine seemed to stumble a little.... Maybe ill throw this item on the replace preventatively list...

 

On the PCV. I just put a new OEM one in a couple days ago. I dont want to open the old to look inside as it was working fine, I just heard how when they fail it can be pretty sudden and catastrophic. Anyway, something must be inside. On both when I tapped them against my hand or such, they vibrate like there is a spring inside or such. Maybe some sorta check valve or something.