The Nissan Path

2009 SE V6 with 90K miles on - immaculate until this happened.

A year ago, the day I planned to propose to my wife I went across the border to US and I filled up my truck with diesel (about 80%) instead of filling it up with gas. I thought the nozzles are different in US... My head was somewhere else I guess

With a lot of smoke and bangs I drove it for about 25 miles at about 15mph to the dealer. They cleaned it up ran it a little and charged me 900. Not bad I thought because I originally thought the coolant leaked into transmission. I drove it and a day later lots of bangs and poor driving - cats failed. Dealer changed for free. Great. Considering it is not under warranty.

It has been a year. The car has been sucking on oil like crazy. I go through a jug of oil every 500 miles or so. It runs well. I have tried thicker oil with no luck. There are no leaks from underside.

Went to Midas (popular mech shop here) they said it would likely be the valve seals but then their mechanic who worked for Nissan for 6 years said that it is the chips that were sucked into the engine from catalytic converters. That makes no sense because they are downstream. But Midas is 80% certain the cylinders have been scraped with these chips and that's how the oil is leaking in.

I am not sure if their theory is correct... Can anyone else chime in on this?
What would you do (no i do not want to leave my car in a parking lot for theft sell it without saying anything)....

Whats my cheapest option...?

Please help....

they may well be correct
a compression AND leakdown test should be next..........

will the compression test tell me if the valve seals are gone? how about the scraped cylinders?

I am surprised Midas never suggested the compression test or the leakdown..

Jimmy777 wrote:will the compression test tell me if the valve seals are gone? how about the scraped cylinders?

I am surprised Midas never suggested the compression test or the leakdown..

won't tell you anything about valve stem seals
valve stem seal issues are very rare
a compression test will tell how much (or little) compression you have
a leakdown test will show where the compression is being lost (piston/rings or valves, whether intake or exhaust)
just getting the spark plugs out to do these tests is quite time consuming, and a leakdown test even more so (may require front engine cover removal)
there are several other threads/topics on this problem
you might try a forum search for more info

The whole pieces of catalyst getting sacked into the cylinders is entirely possible. We've had several reports here.

disallow wrote:The whole pieces of catalyst getting sacked into the cylinders is entirely possible. We've had several reports here.

Good to know its true - though bizzare- i was struggling to find more on this without luck...

eieio wrote:

Jimmy777 wrote:will the compression test tell me if the valve seals are gone? how about the scraped cylinders?

I am surprised Midas never suggested the compression test or the leakdown..

won't tell you anything about valve stem seals
valve stem seal issues are very rare
a compression test will tell how much (or little) compression you have
a leakdown test will show where the compression is being lost (piston/rings or valves, whether intake or exhaust)
just getting the spark plugs out to do these tests is quite time consuming, and a leakdown test even more so (may require front engine cover removal)
there are several other threads/topics on this problem
you might try a forum search for more info

Interesting. Forgive me for the noob question... But what do I really need a compression test for? If the compression was low how would that eat up oil? I am guessing compression during explosion?

I think the leak down test would be far more valuable?

Jimmy777 wrote:Interesting. Forgive me for the noob question... But what do I really need a compression test for? If the compression was low how would that eat up oil? I am guessing compression during explosion?

I think the leak down test would be far more valuable?

if your cylinder walls, piston, and/or rings are damaged by converter debris, oil will go past the piston rings, and on into the combustion chamber, where it will be burned
a compression test is valuable as a general guideline as to the overall condition of the combustion chamber
once the spark plugs are out, it's easy to do
a leakdown test, on the other hand, won't test the actual compression, but by pressurizing the combustion chamber and determining whether the compression is lost either through the crankcase (piston/ring/cylinder issue), or through the intake or exhaust valves (valve or seat issue)
this is much more time consuming, as it has to be done for each cylinder while the valves are closed
this probably necessitates front engine cover removal in order to determine when the valves are indeed closed, because it involves the valve timing in relation to the crankshaft, and I don't think there is an external way to determine this
if your compression is bad, and it's determined that converter failure is the cause, you might as well start looking for a replacement engine and converter system as needed

smj999smj, can you shed more light on this?

From things said on this forum in the past, I get the impression that the cats do not like any misfires that go on inside this engine. It is for that reason I decided to replace the 100k mile spark plugs early and use injector cleaners.
Sounds to me like the cat substance got sucked into the cylinders due to their close proximity coupled with misfires.
I know that adding oil that often is an aggravation, but it only adds a half-cent per mile in cost until you decide what course to take.

Jimmy777 wrote: I go through a jug of oil every 500 miles or so.
Please help....

is your "jug" a gallon?

These engine use the variable valve timing to accomplish EGR rather than a conventional EGR valve setup. It does this by cracking open the exhaust valve slightly during the intake stroke, which draws in exhaust gas directly from the exhaust manifold. If the converter is starting to break down, the catalyst substrate can be sucked into the combustion chamber during these EGR events, which will cause scoring to the cylinder walls...which leaks to poor compression and oil burning. This issue first cropped up on the 2002-2004 Altimas with the QR25DE engine. It's not quite as common on the VQ40DE, but it does occur sometimes. Compression and leakdown test, if needed, would help confirm this.

eieio wrote:

Jimmy777 wrote: I go through a jug of oil every 500 miles or so.
Please help....

is your "jug" a gallon?

3.78 litres - pretty sure its a gallon.

smj999smj wrote:These engine use the variable valve timing to accomplish EGR rather than a conventional EGR valve setup. It does this by cracking open the exhaust valve slightly during the intake stroke, which draws in exhaust gas directly from the exhaust manifold. If the converter is starting to break down, the catalyst substrate can be sucked into the combustion chamber during these EGR events, which will cause scoring to the cylinder walls...which leaks to poor compression and oil burning. This issue first cropped up on the 2002-2004 Altimas with the QR25DE engine. It's not quite as common on the VQ40DE, but it does occur sometimes. Compression and leakdown test, if needed, would help confirm this.

Will print this out and give to nissan dealer when I do the tests
will come back to report here...

CPLTECH wrote:From things said on this forum in the past, I get the impression that the cats do not like any misfires that go on inside this engine. It is for that reason I decided to replace the 100k mile spark plugs early and use injector cleaners.
Sounds to me like the cat substance got sucked into the cylinders due to their close proximity coupled with misfires.
I know that adding oil that often is an aggravation, but it only adds a half-cent per mile in cost until you decide what course to take.

Some of you guys talk about changing the spark-plugs yourself but after looking at the post somewhere here (with colored pics and steps) i think its sort of involved...?

Jimmy777 wrote:

eieio wrote:

Jimmy777 wrote: I go through a jug of oil every 500 miles or so.
Please help....

is your "jug" a gallon?

3.78 litres - pretty sure its a gallon.

Need to revise my math, I assumed it was a quart. Yes, that IS a lot of oil.
As for spark plugs, I had the dealer do it. It seemed rather involved for my skill level.