Dharn55

Just a suggestion, check the cap on the oil filler tube to make sure it is tight and there are no leaks on in the tube. Last spring my car started to through CEL's and would run rough ir with a varying/high idle. I ran checks with my Durametric and got several error codes. I would clear them, the car would run rough for a few miles, then even out, then the codes would come back. Every time I cleared the codes it would run poorly for a few miles then even out, then the codes would come back. I checked for vacuum leaks and could not find any. I cleaned the MAF and the intake, still had codes. I replaced on O2 sensor that was loose, still threw codes. I changed the sparkplugs and checked the coils, but still problems. Then I went to add some oil and found the the filler tube cap was not tight. Tightened it and within a few miles the CEL went off and it has run as smooth as butter for several weeks and almost 2,000 miles on two road trips.

Sometimes it is the simple things that we miss. Worth a try.

Ahsai

BTW, also check between pin 1 and pin 2 of the post-cat O2 sensor with it unplugged from the car. You should see 1.8 - 2.5 Ohm at 20C. That verifies the heating element.

Johan_996

I agree- my experience so far, sending the Porsche to an Porsche mechanic is a high bill but without actually finding the root cause. So I decided to buy my own code reader and try figuring out the root cause. I hope I succeed with it. So far I will start measuring voltage on the wording as suggested I will look into your advice too, thanks

Johan_996

I was in doubt if the previous test of 02 sensors (volt) was completely correct as the car only sat in garage 5-8 minutes to achieve full operational temperature on the engine, 02 sensors and cats. (And i can read that if engine is pr 02 sensors are not fully in operational temperature the 02 volt will be sat to around 0.44 volt by the CPU until proper temperature is reached - is this correct?)

However today I had a window to do a proper long drive and Theo do a test today - and now the data are a different story. The post 02 sensors dies no longer stat at around 0.44 volt. I have added links to both 02 sensor data in volt and Fueltrim values.

I am however not so happy with the test result of the 02 sensors I think. Remember I have 02 extenders mounted for the post cat sensors. The post 02 sensors seems to fluctuate- as I understand this is or could be a sign that the cats are toasted.

But what do you read in the New datastream and Can we conclude anything on these measures yet? Maybe some more tests?

Porschetech3

Looks like your cats are done..... how many miles on them? Have you been running any oil with high ZDDP? or high performance fuel?

Johan_996

i only owned the car for like 1.5 year (don't drive winter) and it had the cel light coming on ever since and I have had it investigated by a Porsche mechanic who couldn't find the foult which puzzles me looking at the data I am now pulling out of my own OBD2 tester.

I don't know if previous owners did some of the things you mention but I wouldn't think so . I am not sure when the sport system was installed. Guess for around 80.000 kilometers ago looking at info I have on the car.

I have seen others complaining that the Dansk sport cats don't last so long so maybe they just got tired over time - if they are toasted that is

Here another test I did today now with graphs + data - graphs are however quite tiny. Engine fully up in operational temperature and at 2500-3500 rpm. 3 minutes test. Cell 420+430 by the way came up again today since my last test, where I erased it.

Macster

P0420 and P0430 arise because the converter associated with the error code is not operating up to full efficiency. The converter is not able to store oxygen.

However, before replacing the converters teh factory reference manual says to if the P0420/P0430 error codes are accompanied by any aging O2 sensor codes to replace the indicted sensors then clear the codes and road test the car. Then if the converter error or errors return replace the indiciated converters.

Normally provided there were no O2 sensor error codes I'd offer the converter or in this case converters are toast (been through this with my 2002 Boxster) but the presence of post converter O2 extenders makes for a more complicated diagnosis.

The #2 O2 sensors want to be and should be in the factory exhaust system right at the optimum location to sample the exhaust gas from the converter. The sensors need to be hot and proper positioning is critical.

With extenders all bets are off. Usually extenders are used with aftermarket converters. Have you tried removing the extenders?

Be sure the exhaust system is leak free.

Last but not least with some OBD2 code readers/data loggers/data viewers you can run some DME resident O2 sensor tests and from the results of these tests often identify O2 sensor problems.

Ahsai

Macster covered it pretty well above. My take is your cats are toast.

Johan_996

ok thanks for the input. Just to be clear: It is an aftermarket exhaust sports system from Dansk. I however guess this doesn't change the fact that the extenders might jeopardize readings in some way - how I don't know. I had the same cel 420 and 430 coming on before I mounted them, so guess chances are low, that I would not have fluctuating 2nd 02 sensor readings without them.

I however also wondered if the extenders would jeopardize the data so might be worth a try to unplug these and do a new reading. I think the probability that the cats are toast is very high - based on all the input from you guys and my growing knowledge of functioning of 02 sensors. Will test for exhaust leaks and maybe dismount extenders - last try before new cats. Thanks allot for all inputs.

Johan_996

that is my take too. Might try to remove extenders to see what happens to sensor readings. Thanks for your input on this.