Calling on 986 Forum Master Mechanics

[Pdwight]

Originally Posted by Cloudsurfer

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.

Can I have your other Porsche sticker for my tool box

[Jager]

Originally Posted by Pdwight

Can I have your other Porsche sticker for my tool box

It’s actually a magnet... Yes you can have one.

[seventythree]

Hi guys,
I'm having the same exact symptoms as Jager with my 02 Bosxter base with 96,000Kmiles.
I have been getting a CEL every now and then for the past year, which I reset using my Durametric.
Problem is I'm due for smog inspection (California) and my renewal indicates that I must take the car to a STAR station. (those who live in CA know what that means.)
So, I reset the last CEL and took the car in. 15 minutes later the tech came to the waiting area and informed me that the OBD indicated that the car wasn't in "Ready" state to be tested. He asked if I had any repairs done, or had the battery disconnected? I said no! I was told to drive the car for approximately 80 miles and take it back for another try.
After 90 miles of driving, I checked the Ready Status and only "Catalytic Convertor Efficiency" was still in Fail state.
After some research on the web, I came across a statement which said, in CA, on 2000 and later cars, with one out of 5 readiness monitors off, the station can proceed with testing the vehicle.
So I go beck to the smog station and they refused to test the car because of the one readiness monitor being in fail mode.
Since, I have driven the car for another 120 miles and the cat readiness monitor doesn't want to go into pass mode. BTW, no CEL either.
Based on the above, I have two key questions:
1) Will a failing cat prevent the respective readiness monitor from resetting?
2) Is it true that I should be able to get the car smogged with 1 of 5 monitors in fail sate?

As always, I would greatly appreciate any and all input.

TIA

[jb92563]

The Cats are designed to last forever basically and this would be true it they never became fouled by oil in the exhaust over a long period of time, excessive temperature (overly rich unburnt fuel getting into exhaust) or mechanical failure of the converter element (rock smashed Cat or Internal cement came apart causing cat element to loose its seal and allowing exhaust to bypass the element).

I had a Cat failure at 75K miles due to the cat element cement losing its seal.
You can hear the element sliding back in forth inside if you shake the removed cat.

I replaced it with a used one from ebay since Dismantler Businesses are not allowed to sell them used in CA. Works better than the other banks cat now and cost ~$250 vs the ~$1800 for a new one.

I used a scope through the front O2 sensor after my AOS failure a few years ago, figuring that I had oil fouled the cats but it looks fine.

[jb92563]

Originally Posted by seventythree

Based on the above, I have two key questions:
1) Will a failing cat prevent the respective readiness monitor from resetting?
2) Is it true that I should be able to get the car smogged with 1 of 5 monitors in fail sate?

They keep changing the rules yearly. In 2015 they don't use the tailpipe sniffer on 2000 and newer cars and only rely on the computers diagnostic report so the CAT condition diagnostic would be mandatory so if THAT subsystem was not showing ready they can not pass your car.

[seventythree]

Thanks jb for your response.
Guys, I'm getting a little desperate here. I've been monitoring the O2 sensor voltages before and after the precat for both banks 1 & 2.
First off, while ideling, both banks look fine. Before cat is sinusoidal and after cat is fairly flat at around 0.8v.
While driving, the after cat voltages are fairly jumpy with bank 2 being a little worse. However, the before voltages aren't consistently up & down and seem to skip a beat quite often.
I am getting desperate because I don't want to spend 6 hours on my back changing out the precats just to find out the problem is still there. (I am a pretty accomplished DIY mechanic but having to wear reading glasses most of the time has taken a lot of the fun out of it.)

To recap the problem, the cat efficiency monitor is stuck in Fail state and won't switch to Pass even after ~300 miles of driving. The other 4 monitors are in Pass state and I haven't got another CEL since I turned off the last one and tried to smog the car 9 days ago. It's a 2002 Boxster base with 96 Kmiles.

Please respond if you can help me diagnose the problem with more accuracy.

Thanks again.

PS, If I let the car idle for a minute or two, the period on the sine wave becomes as tight (short) as we see in most illustrations. However, the period is much longer most other times.

[JFP in PA]

Originally Posted by seventythree

Thanks jb for your response.
Guys, I'm getting a little desperate here. I've been monitoring the O2 sensor voltages before and after the precat for both banks 1 & 2.
First off, while ideling, both banks look fine. Before cat is sinusoidal and after cat is fairly flat at around 0.8v.
While driving, the after cat voltages are fairly jumpy with bank 2 being a little worse. However, the before voltages aren't consistently up & down and seem to skip a beat quite often.
I am getting desperate because I don't want to spend 6 hours on my back changing out the precats just to find out the problem is still there. (I am a pretty accomplished DIY mechanic but having to wear reading glasses most of the time has taken a lot of the fun out of it.)

To recap the problem, the cat efficiency monitor is stuck in Fail state and won't switch to Pass even after ~300 miles of driving. The other 4 monitors are in Pass state and I haven't got another CEL since I turned off the last one and tried to smog the car 9 days ago. It's a 2002 Boxster base with 96 Kmiles.

Please respond if you can help me diagnose the problem with more accuracy.

Thanks again.

PS, If I let the car idle for a minute or two, the period on the sine wave becomes as tight (short) as we see in most illustrations. However, the period is much longer most other times.

If you are throwing P0420 and/or P0430, and you know there is nothing wrong with the O2 sensors, you have bad cats, which are not going the heal on their own. You are also not going to sneak this past the emissions inspection.

[seventythree]

Thanks JFP,
Can you guide me through the process of eliminating the O2 sensors as a culprit.
I just want to tackle the pre-cat replacement project with more confidence.
TIA