Catalytic Converter

[N80]

I have a 2003 Nissan Murano with 130k miles on it. Now the check engine light is on and the dealer says the catalytic converter is 'bad' and needs to be replaced. At $1200. It runs fine. Get a little more smoke than usual when it starts and starts aren't as brisk as when it was new, but otherwise everything is fine.

I'm all for protecting the environment and all that but $1200 is more than I'm willing to spend to keep Al Gore happy.

I live in a state that has no vehicle or emissions inspections (thank goodness).

So, my only reason to replace this thing is make sure the car runs properly. What exactly happens when a catalytic converter goes bad? Does it impeded exhaust flow? If it has no real impact on performance or longevity then I'm not going to bother. If it is important for those things then I'm going to sell it.

We love the performance and form factor of this car; its my wife's. And I've always been a big Nissan fan, but this Murano has not been as flawless as all my others and there's a lot of noise on the web about the catalytic converters going bad on the Murano. So if it really needs replacing its good by Murano, goodbye Nissan and I will have to look elsewhere for an AWD station wagon. Maybe Subaru.

 

[RobertN]

They tend to clog. I had one do that on my old truck. It was on a trip, about 4 hours from home. Got to where it would idle, but no much more. I wound up unbolting the front of the catalytic converter, and driving 4 hours home with an open exhaust.

I fixed it later before a smog check. Until the smog check, I got a bar and punched the stuff out.

 

[ray66v]

As Robert said it is probably starting to fail.

They usually get melted from fuel burning inside.

Baring a manufacturing defect, there is an underlying problem causing the failure. (i.e. some sort of ignition problem).

If it is going, eventually, it will drive like the brake is on.

When this happens there, is a risk of igniting the carpet, and padding.

Start it up cold, and drive it for 5-10 minutes, turn it off, and open the hood. If you hear a lot of metallic popping and ticking noises, the exhaust system is over heated. That means the converter is failing.

Have an aftermarket converter installed, for a lot less money, after the reason for failure is determined, and repaired.

 

[Wis Bang]

Depending on the design you should be able to get a muffler shop [Mineke] to install an aftermarket unit. Speed houses like Jeggs or Summit sell high flow cats for a few hundred, price one on line to get a ballpark for the cost...try NAPA or Advanced Auto Parts on line to get a ballpark; I'll bet you can get one for alot less than the dealer.

If it doesn't plug up the oxygen sensors [before and after] will make the fuel delivery system run very screwy probably making it burn more fuel and run less efficient...on OBD II [post '96] autos it's part of the system and you need to realize it.

 

[kenmac]

when mine went bad. It set the code cat. converter below threshold. Meaning the cat was burn / burning out not capturnig enough stuff.. I didn't replace my cat. To keep the light off I bought a spark anti fouler & installed it where the sensor goes . Then, I screwed the sensor into the anti fouler. This keeps most of the sensor out of the exhaust stream. Caution,,, in some cases you may get another code,,, lean mixture. May be worth a try. I believe it is a 10 mm anti fouler

 

[427ricky]

Just cut it out and put a peace of pipe in place. Take your old cat to the local scrap yard it's probably worth about $100.

 

[westcliffe01]

You should check into whether the Cat has a federally mandated durability requirement. Many systems have a mandated 10 year durability requirement. The O2 sensors are not covered, but the catalyst is. Chrysler / Jeep had to recall and replace millions of catalysts because they were not durable.

Catalysts can degrade at the metallurgical level (sintering of the platinum or palladium) or mechanical (typically the support mat giving out from thermal exposure). The catalyst (precious metal) can also be poisoned by exposure to lead or other metals in the fuel as well as certain oil additives, which should not be in the OE specified oil, but may be in aftermarket products or fuel additives.

OE testing usually has to extend well past 130k, since 150k is the mean distance to failure and that number includes data from much older vehicles.

The only time warranty may not apply is when one has driven for many thousand miles with a check engine light (they can tell by scanning the ECU). Worst case scenario, get an aftermarket catalyst for less than $200.

I have a 2003 Nissan Murano with 130k miles on it. Now the check engine light is on and the dealer says the catalytic converter is 'bad' and needs to be replaced. At $1200. It runs fine. Get a little more smoke than usual when it starts and starts aren't as brisk as when it was new, but otherwise everything is fine.

I'm all for protecting the environment and all that but $1200 is more than I'm willing to spend to keep Al Gore happy.

I live in a state that has no vehicle or emissions inspections (thank goodness).

 

[N80]

Thanks guys. Will look into aftermarket units. I knew they would less expensive but did not know by how much.

I took the one off my first Nissan pickup. It bolted on and I bought a replacement tube ("for racing purposes only") that bolted back in place.

I've never been under this Murano so I don't know if the cat is bolted on or welded on. Even if it is a bolt on there would have to be a manufactured pipe for me to replace it with. I don't weld or fabricate and I'm assuming the muffler shops aren't allowed to pull them.

 

[N80]

Doing a little research. Apparently this car has two catalytic converters. One right at the manifold and one in the rear. (Or maybe it has 3 ???? since its a V6 and has two manifolds????) I wonder if they can tell me which one needs replacing. The aftermarket ones for the rear have no port for the O2 sensor so I'm assuming its the one at the manifold that has gone bad.

Very confusing.

I'd love to pull them off and gut them. What would that do to the O2 sensor and what effect would that have?

Thanks guys. I must say the more I read about this problem with this specific model the more I'm inclined to bite the bullet and get rid of it. I have no car payments right now and I'm no longer into cars and it would stink to have a payment. I usually drive my cars and truck until the die or get totaled but this one is starting to give me a bad vibe. Just got through spending $700 for new front struts and axle seals.

Oh, the emissions warranty is only for 80k miles.

 

[westcliffe01]

Looks like the law requires 10 years / 100k miles for an SUV, so you missed it by 30k miles...
EPA regulation
\5\ At the time this durability procedure was effective, the
useful life mileage for light-duty vehicles was 100,000 miles. Refer
to 40 CFR 86.1805-04 for current useful life mileage values.
On a Japanese vehicle, I would expect you would likely have a fabricated manifold with a close coupled catalyst, with a second catalyst in the "toeboard" or underfloor. Typically the manifold catalyst is a fully welded assembly and requires replacement of the manifold too (its in 1 piece).

If it is not physically damaged, I would suggest going to a non OE service center to have them read the PCM codes. If your O2 sensors have never been replaced thay are certainly due. Usually even getting to 100k is a miracle. My previous Audi needed new sensors every 75k, supposedly regular gasoline here has a high level of sulphur and poisons the O2 sensors.

The first O2 sensor in the system (closest to the exhaust port) is the most critical, but all of them do need to work. If it is O2 sensors that you need it should be $300 at the most for 4 sensors + some labor to fit them and it will run as long as the engine is likely to live.

 

[RonMar]

Yep, it is probably throwing an O2 code of some sort. As mentioned take it to an independent or even to schucks and read the codes yourself(they have readers you can use in their parking lot to read the fault codes). The plugin to connect the code reader is probably near your right knee when seated in the drivers seat.

It probably has two O2 sensors, one upstream of and one downstreeam of the catalyst. If it has two cats, the upstream O2 sensor is probably between the cats. I have never seen a code or sensor for a cat, but reading differences between the two O2 sensors can tell you what the cat is doing. Even if you dont have emissions testing requirements, simply removing the cat may not allow the two O2 sensors to read something they are happy with, and even with good upstream and downstream O2 sensors, you still may get a trouble code...

How old are the O2 sensors? If original, probably best to figure replacement sensors into your bill somewhere. As mentioned, 130K is a good long life for something that lives and breathes in the exhaust stream of an internal combustion engine

Good luck.

 

[WVBill]

As folks have said, and I can attest from recent experience, within a few months if this is your daily driver, the cat converter will get almost completely plugged up and will so restrict flow of exhaust that your call will not pull under load.

Something has caused your cat converter to fail. In my case, I ran my Pontiac Vibe 180,000 miles without a tune up (dumb me - but it always seemed to run fine). Eventually the spark plug gap got so wide that it was dumping un-burned fuel into the cat which caused it to fail. After replacing the cat, only then did it throw a check engine code that indicated running rich.

 

[N80]

That's the odd thing though. This car runs fine. Gas mileage is as good as it has ever been, maybe better. But, I need to do a few things. First, all of this info is second hand from the dealer via my wife. I need to talk to the dealer, although my wife says she has a written description and estimate that I need to look at. Second, I need to find someone else to do this work. This dealer is occasionally a little shady and always far more expensive than everyone else. Got the struts and axle seals done by a reputable guy for literally half the cost of the dealer. I think I need to get a second opinion from him since there is no obvious evidence that anything is impeding exhaust flow at this time.

 

[ray66v]

That's the odd thing though. This car runs fine.

It only takes an intermittent misfire on one plug. You can easily not notice it happening.

This could be from lots of things; a bad wire, bad coil, bad plug.

Did you do the metallic noise test I suggested?

 

[WVBill]

I had my dealer replace the cat on mine. He's very trustworthy. Price was $455 parts + Labor. I checked on-line and an after-market cat converter for my car ran around $375 so he was fair with me again.

My car ran fine too - until one day when it barely made it up the mountain I drive over each day (8% grade).

 

[N80]

It only takes an intermittent misfire on one plug. You can easily not notice it happening.

This could be from lots of things; a bad wire, bad coil, bad plug.

Did you do the metallic noise test I suggested?

Yes, I don't really hear much other than the typical cooling down noises it has always made.

So are you saying the cat could be damaged because of a recurrent misfire? I understand how that might happen but the diagnostics should indicate that as well I would think.

I'm getting a check engine light on my son's old Maxima and was told it was misfiring and they were able to tell which cylinder it was from the diagnostic. Of course they couldn't say if it was a plug, wire or coil. Anyway, if that was happening on the Murano I hope they could tell that too. Would hate to replace the cat and then have a continued misfire problem.

You know, I hate to sound like an old man, but I got well over 160k miles on my first Nissan pickup with a four banger a carb and a mechanical distributor. Never had a problem with it (until it was totalled). Not sure what we're gaining with these high tech engines. I'm pretty sure I know what the dealers are gaining with them.

 

[N80]

RonMar, do the O2 sensors provide any performance or durability benefit? I don't care if the check engine light stays on. What I'm getting at, is if I hollowed out or replaced the cat with a tube, will the abnormal readings from the O2 sensors cause any problems other than emissions problems and a check engine light?

 

[kenmac]

You can buy a cheap code reader for about 60-70 bucks @ most auto parts stores. It will tell you which cat is bad as in bank 1,2 etc, you can also clear the code & see how long it takes to come back on. The computer shouldn't be making any engine adjustments.So, it should be running just fine. Just letting you know the cat is bad.. Stay away from the high flow cats. My son had his factory cats taken off for high flow cats,. His sensors are now throwing bad cat codes.

 

[RobertN]

That is exactly what happened to me. Was four hours from home, going over Buckhorn Summit, and it seemed a little sluggish. Next day continued up the hill to Weaverville(North Calif), and barely rolled in to town. Literally, made the last half mile in granny low('89 Ford F250 with a 351).

My car ran fine too - until one day when it barely made it up the mountain I drive over each day (8% grade).

 

[dmccarty]

This is bringing back nightmares.....

My wifey bought a used Volvo. I think it was a 98 V70 station wagon...... I will skip the engine rebuild....

We have emissions inspections in NC. The Check Engine light came on in the car and the fun began. No way to pass with the light on. No passed inspection then you do not get a registration. :confused2:

We knew a GREAT Volvo mechanic. The Check Engine light would pop on because of the O2 sensors and the Cat. Somehow the mechanic got the car to work long enough to pass the emissions inspection but a couple of months later the Check Engine light was on again. This time we had to replace the Cat which we did with an after market unit for a fraction of the cost. The mechanic did say the Volvo units were better but given the age of the car we were not going to spend the dollars.

The old cat is sitting waiting to go to the junk yard. Course it has been waiting for a couple of years and I wonder when SWMBO will take it to the junk yard.

Later,
Dan