The engine is using/burning an unusual amount of oil and somehow is affecting the catalytic converter.The mechanic says even if we replace the converter to pass emissions test that in another year or so, it will happen again.He says some 2001 Altimas just have this problem.Have you heard of this and is there any solution?

hi.
first thing to do is change the air filter. even if it appears clean, the airflow can be blocked enough to affect the petrol air ratios in the engine which will give high HC readings.
changing the spark plugs can give a cleaner spark, and better ignition, with lower HCs. high HCs could also be caused by traces of oil getting through worn piston rings and valve stem seals and burning in the combustion chamber. there are many oil additives that can help stop this and reduce HC levels as well.
hope these suggestions help

Hi,
The code indicates a fault detected in the catalytic converter (bank1). It could just be an oxygen sensor, but if your truck is over 6-7 years old, I would say you need to replace the converter.You could try a new upstream O2 sensor on the left cylinder bank manifold first, it will be much cheaper if that would be the cause.....Mike

The used engine that you bought was previously damaged by the disintegrating cats that were on the car that it came from and because it was burning oil badly when you installed the new cats, it ruined the new cats with the oil that was coming out of it. You'll need a re-manufactured engine, not a used one, they are all bad, and new cats again. Bad news I know. but likely the problem.

Your car does in fact need a new catalytic converter. And it should also not burn a drop of oil. It can burn oil as it seeps past leaking intake valves and piston rings.

I highly recommend you do not even start the engine again until the exhaust and intake valves have been inspected and replaced as needed, it has a new catalytic converter and a complete tune up.

Wipe off the lid and check it again. I have been working on cars for over 3 decades and have never heard of such a thing. Catalytic Converters use platinum coated ceramic pellets to convert nasty combustion byproducts into less nasty products. The exhaust from the engine comes in one end and goes out the other end toward the muffler. The extremely high temperatures involved would burn off any oil, and introducing any would actually increase the amount of emissions rather than reduce them, which would be entirely pointless. Read the last paragraph of the attached article.
http://autos.yahoo.com/maintain/repairqa/battery_electrical/ques083_0.html

Hello my name is Ben. One quart isn't unusual, two is a bit high. However if it runs great as you say I wouldn't be overly concerned. I will ask you how many miles you go in between oil changes. I'm still "old school" on the 3000 mile oil change even though manufacturers are no longer recommending it. The longer oil stays in your engine it gets dirtier. The oil absorbs tiny particles of carbon from the combustion. Even though these particles are very small, they can actually get in between the pistons and rings and cause oil loss. In other words as the oil gets dirty, the engine tends to use more oil. If you are changing oil at 4000 or even 5000 miles, I would suggest changing it at 3000 miles and see if it uses less. I hopes this gives you some information that is helpful. If you have any other questions feel free to ask, Ben.

I will make an assumption here, we know what the root word means. This code was extracted from the computer by? What this is telling you one of 2 things: The Bank 2 oxygen sensor down stream of the catalytic converter (there are 2 converters, one for each bank of cylinders on the 4.6ltr engine) is bad and/or that the Bank 2 catalytic converter is no longer doing the job it was designed to do. Simply, Catalysts wear out. They are good for approx 100,000 miles (as required by Federal Law). Again, I assume that the reason the intake manifold was replaced was because it had a crack in one, or more, of the runners? (part that feeds the head of a manifold). It may have taken a while to find this as being the cause of why the car running incorrectly, maybe rough. This means, that during the time the car was being driven with the problem, the amount of unburned, or not within spec exhaust gases, coming off the side of the engine affected by the intake issue was higher than normal. This out of balance level of exhaust gases were being dumped into the converter on that side of the engine, thus causing the converter to have to run hotter, work harder, or even at the time the gas was being processed through, causing deposits to be formed in the converter, thus shortening it's life span. The Bank 1 side of the engine, apparently, did not have the issue and it's catalytic converter's life was not affected. I hope this makes sense to you.

Was a leak down test performed on the motor?This will determine if the oil loss is due to bad rings or a head gasket.A head gasket can be repaired,rings will require an overhaul or new motor.Have checked the coolant for oil contamination?

check engine light has nothing to do with oil level. Only the red engine light does. It sounds like you are burning a lot of oil and it is poisoning your catalytic converter. Your converter is killing itself trying to treat all the unburned oil that is coming to it. It will get so hot that it swells inside and clogs it up. Why you are burning oil is the question. Only 3 possibilities. Past the piston rings, past the valve stem seals or a plugged pvc valve and its hoses. Clean the PVC hose and change the PCV first. Changing the cats now will just kill them again until you fix the oil burning.
Autozone will do free scan test for fault codes by the way.
PCV won't show up there though.
You can buy cheap engine on ebay or at car-part.com. page with asterisk is lowest price.

Somehow raw gas vapor is exiting one or more cylinders and being burned inside your catalytic converter. You'll ruin another expensive converter if you replace that before the problem is solved.

Has your mechanic checked the engine timing?