Calling on 986 Forum Master Mechanics
 

I have an intermittent P0430 alarm that has been haunting me for at least four years. It hid for a little while last year but has come back to annoy me. Attached are pictures of O2 sensor voltage levels ahead of the catalytic converters (both banks) and O2 sensor voltage levels behind the catalytic converters. As you can see there are somewhat erratic O2 sensor voltage level changes behind the catalytic converters on bank 2. The voltage may stay consistent (similar to bank 1) for a while and then the voltage will drop a few times and smooth-out again. What can cause this? Wouldn’t the inconsistency of the voltage drops exonerate the catalytic converter? Can a vacuum leak cause this condition on one bank?? The O2 sensors are just over 2 years old, with ~35,000 on them... I’m thinking swapping the sensors or replacing the O2 sensor behind the catalytic converter on bank 2. Any other suggestions or advice would be greatly appreciated.

http://986forum.com/forums/uploads01...1373516237.jpg
http://986forum.com/forums/uploads01...1373516268.jpg
http://986forum.com/forums/uploads01...1373516298.jpg

Thanks

When you get the sensors ahead and behind the converter drawing similar lines (one should be a sine like wave, the other relatively a straight line), which you appear to have, it is the sign of a dying cat. I'm away from the shop at the moment, but I can show you curves for good and bad converters, yours appears weak at best.

What! I need to replace a catalytic converter with only 246,000 miles on it?

How did the cats perform on your last CA smog test?

Passed with flying colors two years ago... I have to get a smog this month for August registration.

Since I am not getting a CEL (the P0430 shows-up in memory... Sometimes weeks later after clearing) (and yes the CEL works) I will probably go ahead and take it to a Smog Shop and see what happens.

I would be interested to see what a healthy o2 reading looks like as well so I can compare with mine

OK, here ya go:

Good cat:
http://i1140.photobucket.com/albums/...ps6728ac22.jpg

Bad cat:
http://i1140.photobucket.com/albums/...pscd3fb45b.jpg

Thanks JFP.

I filled my tank with gas that has Techron, and added some injector cleaner, then drove it hard a few times (hit 7K RPMs a few times) that seem to help a little. Here is a snapshot of Bank 1 (no appearance of issues):
http://986forum.com/forums/uploads01...1373838397.jpg

And here are a few snapshots of Bank 2:
http://986forum.com/forums/uploads01...1373838485.jpg
http://986forum.com/forums/uploads01...1373838507.jpg
http://986forum.com/forums/uploads01...1373838524.jpg
http://986forum.com/forums/uploads01...1373838540.jpg
http://986forum.com/forums/uploads01...1373838571.jpg

It seems the catalytic converter on bank 2 is starting to go... Woe is me...

Unfortunately, it would seem so; that last snapshot tells the story as the two sensors are trying to follow each other. Sorry.

Please excuse my ignorance but how do you know it's the cat and not the o2 sensor itself? TIA

I have a CAT for one side never used if you are interested.

Yeah, I'm not done playing with this... I will probably swap the O2 sensors to see what happens.

BTW the Jägermobile just passed the California Smog Test this afternoon. The hydrocarbon (PPM) was 5 (max allowed is 100 idle, 130 at high RPM) (average for passing vehicle is 17) and the carbon monoxide was 0.00% on both measurements. The %CO2 measured was 14.06 and %O2 measured was 0.5. The Jägermobile is still a clean running machine.

Thanks for the offer, is it a TWC for bank 2?

I have a related situation and question. My last two CA smog tests were close to failing. The max HC at low rpm is 58ppm; both tests, one this year and another two years ago, showed my '98 low mileage Boxster at 57 ppm- too close for confortable.

This year I did the following as suggested on this forum: replaced spark plugs, ran two tanks with techron, and drove the car harder than normal. The car was hot upon delivery to the test station.

What might be the cause of the high HC measurements ? Is there a systematic approach to eliminating various causes ?

Several things possible; dying cats will definitely do it, as will leaking injectors, or aging O2 sensors. Get the car scanned on a Porsche specific system like the Durametric used above, it will allow you to check the functions in real time.

Update, I finally got around to swapping the O2 sensors behind the catalytic converters and no change, I am still seeing the same voltage drops on the O2 sensor on Bank 2... Darn it.

I have Porsche Boxster 2.5 1998 and it has failed the emission test on to high Co. The car has been serviced including fuel filter, plugs, oil, air filter, oil filter and coil packs. In addition to this its had new Cats, new o2 senors and I have cleaned the Air flow mass sensor. There are no error codes coming up, have you any idea why the ecu is providing to much fuel so its pushing up the Co emissions? I have cleaned the air system and I have mixed the petrol with injector cleaner, could this cleaner affect the readings? Please can you help? I saw your post and have a similar problem but with the Co. In you search for you problem have you found anything similar to mine and if so can you help.
Thank you

I have never had an emissions level problem, just the CEL with P0430 code which seems to be a catalytic converter starting to fail. I have not come across a similar problem as yours, it might be a fuel injector issue or MAF sensor issue? Have you cleaned the Throttle Body? How is the idle and driving performance?

OK, so I got a fourth mortgage and purchased the factory manifold catalytic converter for my car, I plan on installing it tomorrow. Any recommendations on removing the original bolts on the original catalytic converter would be greatly appreciated.

Thanks
http://986forum.com/forums/uploads01...1383875169.jpg
http://986forum.com/forums/uploads01...1383875192.jpg

Make a concoction of acetone and auto tranny fluid, one to one (I said tranny, heh, heh) and spray all fasteners while they are hot. Easy when loosening. If the fastener is stuck, try some taps with a hammer, then try tightening the fastener. I know it sounds crazy but sometimes tightening will break the fastener free.

I would set your torque wrench at twice the torque spec for the fastener and tighten, loosen the fastener until the torque wrench clics and if doesn't come loose, try some more solvent and taps. Take it easy, many horror stories of having to drill out and tap the manifold bolts.

If no luck, then a torch to heat up the fasteners may work.

Ouch ! I had a set that came off the D-mobile with barely 18k miles on them - that I practically gave away ! Where were you ?

You should have held on to them until I needed them... What were you thinking??

Not to make you feel any worse, but it would have been my pleasure to have given them to the Bard of the 986 forum.

I am honored by your words and thoughts of generosity. You did not make me feel worse, you brightened my evening! Thank You.

san rensho,
You are confirming an email that I received from a good friend that contained University test results of the tranny/acetone mixture, PB Blaster, Liquid Wrench, and different oils. The results showed the acetone and transmission fluid mixture out-performed all other fluids for removing corrosion and breaking bolts loose. Looks like I need to go buy some acetone.
Thanks

Replaced the catalytic converter on Bank 2 (Driver Side) today, I had no problems removing the old bolts. I installed new gaskets and new bolts (anti-seize on the threads). Using Durametric I see a slight difference in the O2 sensor voltage behind the converters. On the new converter the voltage is now flat-line and higher than it was (see earlier posts). In comparing all the O2 sensor voltages there is a difference, I am wondering how much longer the other converter (Bank 1) will last? Any bets on when I get an alarm on that side?:eek:





http://986forum.com/forums/uploads01...1384049080.jpg

Those graphs look really good. Just keep monitoring the other after cat o2 sensor and replace the cat as necessary.

Just out of curiosity, my understanding is that a bad cat doesn't cause any driveablity problems, so why spend big bucks to replace it?

No drivability issues but I live in California... The smog laws are tough and don't allow modifications unless authorized by California Air Resources board (CARB). There is only one aftermarket catalytic converter approved by CARB for the Boxster and that company is not making them at this time, so I had to buy factory converter to continue registering the vehicle... Legally.

Ouch. I live Republican Florida where we don't have no gub'ment intervention. We can pollute at will because there are no yearly emissions tests.

By the way, did you use the acetone tranny fluid to loosen the fasteners?

Yes I did, thanks for the advice.

A big THANK YOU! out to JFP for your assistance on this, I learned more about the O2 sensors and catalytic converters... Buy them from Sunset!!

Given your mileage, I wouldn't even dream of only replacing one side header/ cat.

Replace both cats and at least both pre-cat O2 sensors.

As to the bolts, while I have yet to have one shear off in a head, def take your time and use a quality penetrating oil like PB Blaster.

All O2 sensors were replaced not too long ago.

Spending $4000 to replace both manifolds on a car that is worth not much more than that on trade-in is a little hard for me to justify. I'd rather spread the pain out over time, maybe replace the other side in four to six months. If I lived in another state no problem, there are many choices on after market catalytic converters at a fraction of the cost.

Hey guys, I'm kinda in the same boat as Jager. I've had code P0430 on and off for about a year now. The CEL seems to only come on when I'm driving slowly in traffic or parking structure. I used a OBD2 bluetooth adapter and the Torque app to gather some data. From what I understand, the O2 sensor after CAT should be a relatively flat line around 0.7V. My O2 voltages look pretty bad, don't you think? I haven't had a P0420 on bank 1. I'm trying to find out if my bank 2 CAT is going bad or not in the near future.
http://986forum.com/forums/uploads01...1431377415.jpg
http://986forum.com/forums/uploads01...1431377436.jpg

Forgot to add RPM graph, the time span is about 4 minutes.
http://986forum.com/forums/uploads01...1431378536.jpg

Looks like you've got dead cats. Itsnotanova may be able to fix you up with some used cats. New are very expensive. See Timco, it's not true that the only good cat is a, well, never mind.

Why not peel off a set of these from a low mileage wrecker? I see them on Ebay now and then.

EDIT.

Did not see that this thread is from 27 B.C.

You can probably find a used cat from various suppliers. Make sure it is guaranteed and that they will replace it if it doesn't do the thing it is supposed to do! The job is an easy one, you need new gaskets and that's all.

Update
 

So far the cat on Bank 1 is hanging in there (original catalytic converter), I have over 277,000 miles on it!

Oh no... I just got a P0420 error code. Over 284,000 miles on CAT bank 1.