I have 120 k on my 06 pathfinder le. Recently I have oil smoke on cold start up. After its warmed up, no smoke on any re start .. Only when it's cold. Any ideas ?

That's typically the symptoms of bad valve stem seals, but I've yet to hear of a VQ-series engine that has had failed valve stem seals. I think I would start by smelling the oil for gas and performing a fuel pressure leakdown test. Perhaps an injector is leaking down? That would cause black smoke, as opposed to blue-ish, oil smoke, but would at least rule that out as a possibility and a lot easier than replacing valve seals on a VQ. Perhaps someone else has some other ideas?

Ok, I've been watching the oil consumption. I'm using about 1qt every 5-600 miles. I did replace the PVC valve and hav switched to 20 / 50 oil and that seems to help. This all started after a shop did a Motovac cleaning, what ever that is.
Also, I did have the injectors checked. They flowed with in spec.
Anyone have any ideas?

Though others on this site may disagree, I've had really good success with Lucas Oil Stabilizer. I would suggest using this product at your next oil change.

Do you use synthetic oil?

I use valvoline 20 / 50 synthetic blend. I have tried the Lucas oil stabilizer and I'm not convinced its worth using. I've just never been a fan of a cure in a can

NVRDONE wrote:Ok, I've been watching the oil consumption. I'm using about 1qt every 5-600 miles. I did replace the PVC valve and hav switched to 20 / 50 oil and that seems to help. This all started after a shop did a Motovac cleaning, what ever that is.
Also, I did have the injectors checked. They flowed with in spec.
Anyone have any ideas?

I'm pretty familiar with engines and if you are "burning" a quart every 500 miles and you have smoke out the tail pipe, you got a problem. Sorry man, running thicker oil is not going to get you by for much longer.

staynlean wrote:

NVRDONE wrote:Ok, I've been watching the oil consumption. I'm using about 1qt every 5-600 miles. I did replace the PVC valve and hav switched to 20 / 50 oil and that seems to help. This all started after a shop did a Motovac cleaning, what ever that is.
Also, I did have the injectors checked. They flowed with in spec.
Anyone have any ideas?

I'm pretty familiar with engines and if you are "burning" a quart every 500 miles and you have smoke out the tail pipe, you got a problem. Sorry man, running thicker oil is not going to get you by for much longer.

+1

NVRDONE wrote:Ok, I've been watching the oil consumption. I'm using about 1qt every 5-600 miles. I did replace the PVC valve and hav switched to 20 / 50 oil and that seems to help. This all started after a shop did a Motovac cleaning, what ever that is.
Also, I did have the injectors checked. They flowed with in spec.
Anyone have any ideas?

Motorvac is a top end cleaning system, designed to remove carbon and varnish from the tops of the valves and clean the inside of the intake manifold.

Now I'm hearing that when a cat fails, the sub straight can be sucked back into the cylinders causing an oil burning problem.
Any thoughts on this? Can I use some kind of an additive or are we talking engine rebuild ?

The substrate can be sucked into the combustion chamber as it uses the valve timing to accomplish EGR rather than use a conventional EGR valve. For EGR, the exhaust valve will be opened slightly during the intake stroke to let some of the inert exhaust gas back into the combustion chamber. If the catalyst substrate enters the combustion chamber, it will score the cylinder walls. This was a major problem on the QR25DE engine in the 02-04 Altimas. It is not as common on the VQ-series engines, but I have heard of a few cases.