catalytic converter going bad

okay so i just went through replacing the oil separator and maf sensor to solve a bunch of running and smoking issues, but now ( after about 200 miles) i have another check engine light for the cat. The car runs great still, but does anyone have any suggestions on replacing this part and what it will cost ( auto zone couldnt even order it) I was thinking of getting a bypass but could that make me lose back pressure?

... cats go bad.
What makes you think that's the case?
What's the error code?
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

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the code reader said it was running below normal or something like that
cant remember the exact code. i will try and get it tomorrow. But i was thinking that all the smoke and stuff that was coming out of the exhaust because of the oil separator issue may have burned up the cats

i dont think so.

true those things are expensive, can they be visually inspected?

..but dont panic yet.

excessive exposure to contaminants which coat their catalytic material. Typically a lifetime of burning oil.

Cat health is measured by taking an O2 reading before and after, an subtracting. So a bad O2 can cause this. I'm sure other things can too.

Diagnose, diagnose, don't replace (yet)

Grant

Not knowing the year, or miles on the car, you might consider replacing the fuel injector o-rings(about $75 in parts) on the car. When the seals deteriorate, they can cause a whole host of emission related CELs which are a bear to track down. I put a Fabspeed cat bypass on our 01(base) and love it. Also, you might consider going back and posting the specific CEL.
regards

Quote
skyline_drive
okay so i just went through replacing the oil separator and maf sensor to solve a bunch of running and smoking issues, but now ( after about 200 miles) i have another check engine light for the cat. The car runs great still, but does anyone have any suggestions on replacing this part and what it will cost ( auto zone couldnt even order it) I was thinking of getting a bypass but could that make me lose back pressure?

A converter can be bad. They can fail at any time but very rarely do they fail at least before 80K miles or whatever the miles that the federal/state emissions laws/rules require the automaker to warranty these items for.

But read the codes and post them here. Be sure you have an OBD code reader that can read more than one code. Sometimes there can be several error codes associated with the check engine light. One (or sometimes more) error codes can also trigger the storing of freeze frame data which is a kind of a sensor/derived value snapshot at the time the error was detected and the error code logged.

If the error code is P0430/P0420 the trouble-shooting guidelines state that if any O2 sensor aging error codes are also present to replace the indicated O2 sensors and clear the codes then drive the car a while. If the P0430/P0420 error codes come back, the indicated converter is bad.

Maybe.

You can try a few things: 1) Simply give the engine/exhaust time to burn off any residue from the oil the engine/exhaust system was subjected to from the failing AOS. 2) You can help this process by running a bottle or two of Techron through the gas tank as per directions on teh bottle. Techron will clean the fuel system removing deposits from the injectors (which will improve the spray pattern of the injectors), cleaning the valves (the back side/intake side of the intake valves can develop a build of deposits that can really interfere with the proper flow of air and injected fuel into the chambers), removing deposits from the combustion chamber surfaces, removing deposits from downstream of the combustion chamber and even down to the #1 and #2 O2 sensors, and in between these even the converter working surfaces. I know, this Techron sounds like a miracle fluid but give it a try. A bottle or two is a lot cheaper than a new converter or two. Anyhow, 3) Along with (1) if due on miles (or possibly time) change the plugs and renew the engine air intake filter unless it is fresh. 4) Be sure the oil is fresh (relatively fresh) the engine is not overfilled with oil. Old (contaminated) oil or an engine with too much oil (or the wrong kind of oil, the wrong viscosity grade) can still manage to get past (in the form of oil vapor) a perfectly fine AOS and this oil vapor is routed to the engine's intake and ultimately burned in the engine or in the converters under some conditions. You want to minimize the amount of 'converting' the converters have to do.

(P0420/P0430 ultimately arise because the engine controller has detected based on 02 sensor readings over time the indicated converter is unable to store (enough) oxygen. If it needs less oxygen to perform its conversion processes because it has less heavily loaded with hydrocarbon exhaust gas stream to process then this lowers the converter's oxygen budget and it might begin to have enough oxygen to perform its job and the error codes stop appearing.)

In the meantime buy name brand gas and from a busy station. I know I know it sounds snake-oilish, but my experience with my 02 Boxster is this: 1) The error code is more likely to appear when I resort to using say Rotten Robbie or USA gasoline vs. Shell, or Chevron. I fall back to using Rotten Robbie or USA gasolines though because they both sell gasoline 5 or more cents per gallon cheaper than Shell/Chevron. 2) The P0430 error code is more likely to appear in cold weather even though as best I can say my driving pattern changes very little from season to season.

Using a combination of the above I have managed to nurse along a weak(ening) converter now for several years, managing to get the car through emissions testing with while not flying colors low enough emissions to pass the tests.

Attempting to address this converter problem with an exhaust modification is risky because so many of these in some way violate the requirements for good proper exhaust gas flow and the aftermarket converters (which may be more cheaply made -- read have less of the very expensive catalytic metals in them) do a too poor of a job on the exhaust gases and the error code comes back or the exhaust gas flow is such that the O2 sensors do not function properly and error codes for these appear.

Sincerely,

MarcW.

thanks a bunch Mark, I will try that techron and reset the code. It does need some new plugs and filter so that will be my next project.

I think the warranty on CATS is like 10 yrs.

First, I did not understand what I saw so if anyone can fill in the blanks, please post.

My tech showed me some sort of output graph on the Porsche computer and what I saw was a sine wave in real time. The computer was attached to my running 2000S. The tech said that this sine wave was a failing cat but not to do anything until the check engine light came on. He said that a healthy cat would produce a straight line. At the time, the cat had about 150K miles on it.

Any ideas what I was looking at?

By the way, can't you get a used cat from a dismantler such as Parts Heaven? Gotta be a market for them when a low mileage Porsche meets a tree.

Quote
Bruce In Philly (175K+)
First, I did not understand what I saw so if anyone can fill in the blanks, please post.

My tech showed me some sort of output graph on the Porsche computer and what I saw was a sine wave in real time. The computer was attached to my running 2000S. The tech said that this sine wave was a failing cat but not to do anything until the check engine light came on. He said that a healthy cat would produce a straight line. At the time, the cat had about 150K miles on it.

Any ideas what I was looking at?

By the way, can't you get a used cat from a dismantler such as Parts Heaven? Gotta be a market for them when a low mileage Porsche meets a tree.

What you were probably seeing is the #2 (the sensors after the converters) voltage levels in real time.

Now the voltage levels can vary a tiny bit -- indicating more or less oxygen content in the exhaust gases compared to the ambient air -- which is normal since the air fuel mixture is constantly being made a bit rich to a bit lean (in terms of the what the converters require as ideal which is 14.72:1 for at this air fuel mixture ratio if the engine/et al is working properly the converter is most efficient at processing harmful exhaust gases into less harmful gases).

When the #2 sensor voltage levels start to swing too widely, mainly dropping from 0.7 volts (or thereabouts) to something lower (down to 0.1 volts sometimes in the case of my car) this is a sign the converter is unable to store oxygen (during the 'lean' phase of the mixture variation I mentioned above for use in the 'rich' phase) and this signals the converter is wearing out.

If this swinging gets too wide the engine controller will store an error code and turn on the check engine light.

The tech is right as long as the check engine light is not accompanied by any other signs of engine distress. Unlikely but just wanted to get this out there. I'm sure if the engine started acting up you'd do the right thing.

Even if the check engine light comes on you can do a few things to possibly gain some more service life from the converter. I won't cover these unless you want me to via PM or I guess here, up to you.

You might get a used convertor for your car from Parts Heaven. I have thought about it.

What holds me back? Well, a problem is that in removing the old exhaust manifold one or more bolts that hold the manifold to the head may twist off. These have not been removed in my car's case (and 02) since sometime in mid 2002 when the car was in for a RMS repair (under warranty).

Anyhow, my tech sources tell me that these broken bolts happen so often they have to budget for them when any exhaust work is done.

Case in point, well sort of, is when I had my Boxster in for its its VarioCam solenoid/actuator problem a while back in removing the passenger side exhaust system an exhaust manifold bolt at the flange that connects the exhaust manilfold to the exhaust pipe broke and took the tech extra time to address. All new fastener hardware was ordered and used too (which is ok by me for I would have asked new hardware be used had I been asked).

Even though I'm capable of doing the job, and capable of removing a broken bolt should one break, since I do not have a place to work on my car if this happened I'd be in a bind with the car parked in my employer's shipping bay (where I park it when I do oil changes and where I would park it to do the exhaust manifold/converter R&R) while I worked to get the broken bolt fixed.

But Parts Heaven would be where I would first go I think. (It is located just a short distance (a bit over a minute's drive) from my office.)

A new exhaust manifold with the converter is last time I priced it over $1000 and then the labor if I elected to have this work done at the dealer is another couple of hundred or so. I have not priced at least I can't recall doing this the cost of a used exhaust manifold/converter for me car from Parts Heaven.

Oh, another point: That at 150K miles (your car) or 242K miles (my car) the 'new' converter and the other original one might be so different the engine controller would have to adapt quite differently from bank to bank. It can do this but the engine might not perform as well as it would if both converters were in good working order and about the same 'age'.

OTOH, the engine controller has to adapt to the way they work now, one ok the other not (oftentimes anyhow) so maybe my concern above is overblown?

Anyhow, if you go the Parts Heaven route you might ask what 'warranty' you get with the used manifold. If the thing proves to be worn out or damaged (mechanically) and doesn't perform any better than the one you have (or proves to be worse that the one you have now) would Parts Heaven give you credit towards another? The bad unit can be sold for its catalytic metal content though the net from this sale wouldn't nearly cover the cost of another used one let alone a new one.

Sincerely,

Macster.