Need help with CEL diagnosis

[KS-CS]

I have a 2006 Cayman S Tiptronic with 43K miles; recently it has been throwing the CEL codes shown in the picture below, but it seems to occur only when I am pulling a fairly high-G or sustained right hand turn and RPMs go above 4000 rpms (i.e. on the track). As the codes show, it only involves the bank 1 cylinders (which I believe are on the right in a Cayman). I don't seem to be able to reproduce it by normal driving around town, or acceleration above 4000 rpms in a straight line. The other day, I also got some misfire codes for cylinders 1-3, under the same circumstances (sorry, didn't get a screen cap). I do not notice any change in the way the motor runs (certainly no stuck lifter sounds or rough idling,etc.). I just changed the oil again, and that didn't seem to help. I am planning to replace the spark plugs this week, though I doubt that it would be related to that.

Does anyone have any suggestions as to what might be causing this, and/or why it only occurs on exiting hi-G right hand turns?

[Loren]

P1351 Valve lift control, cylinder 1 - above limit

P1353 Valve lift control, cylinder 2 - above limit

P1355 Valve lift control, cylinder 3 - above limit

Possible fault cause

- A valve does not switch to large lift

- Several valves (various cylinders) do not switch to large lift

Several cylinders may be stored as faulty, although only 1 valve on one cylinder is faulty.

In order to guarantee safety during repairs, the flat-base tappets of the inlet valves of the entire cylinder bank should be replaced if a fault occurs.

So this bank is not switching to large lift as it should. This occurs at WOT.

[KS-CS]

. . . Several cylinders may be stored as faulty, although only 1 valve on one cylinder is faulty.

In order to guarantee safety during repairs, the flat-base tappets of the inlet valves of the entire cylinder bank should be replaced if a fault occurs. . .

That sounds a bit ominous - I was hoping maybe it was just a faulty sensor or something. I hope this is covered under my (non-Porsche) extended warranty . . .

[Loren]

I assume you cleared the codes to see if they would come back?

[KS-CS]

I assume you cleared the codes to see if they would come back?

I did - however it only seems to return under a combination of lateral g-load and high revs; cruising around town it is fine. I wondered if it might be due to faulty coil packs, so I replaced them all, along with new spark plugs. Even with that, I got a misfire code on cylinder 3 today when I tried to reproduce the condition on a freeway cloverleaf ramp. I'm off to the track tomorrow to see what happens. If it recurs, then I'll be taking it into the dealer on Monday to have them look at it.

[KS-CS]

**UPDATE**

Problem solved - after 5 1/2 weeks in the dealer's service dept! It turns out that the problem was the right side primary cat was partially bad. It wasn't bad enough to cause a problem or throw a code under normal driving conditions, but under high load/flow (i.e. variocam range) it was apparently obstructing the exhaust flow enough to affect the valves on the right bank, and cause the lifter and misfire codes. Both headers/cats replaced under the 8 yr/80K mile Emissions Warranty - I am a happy camper again. :thumbup:

[coleta]

Great news. Do you know how they were able to isolate it to the cat.?

[KS-CS]

Great news. Do you know how they were able to isolate it to the cat.?

It was pretty much by the process of elimination - after doing various things like switching sensors, coil packs, actuators, etc. from one side to the other, they had reached the point where they thought that it might come down to replacing the DME, or actually having to replace the whole engine (Porsche was apparently recommending that it might be necessary to replace the engine, rather than tear it down to look for a mechanical problem)! They finally decided to take a look at the cats directly by removing the headers, and that's when they noticed that the right side was partly bad. Replacing it cured the problem.

[Loren]

A very unusual (and perhaps unique) problem I think.

[wvicary]

Can you tell us in what way the cat was damaged? Was the substrate broken/missing or was it melted, and if so, what caused the damaged to the cat? I'm very surprised you didn't get a cat convertor efficiency code.

[KS-CS]

Can you tell us in what way the cat was damaged? Was the substrate broken/missing or was it melted, and if so, what caused the damaged to the cat? I'm very surprised you didn't get a cat convertor efficiency code.

I'm not sure of the specifics, other than there was visible damage of some of the cat element. Some of the early 06 Caymans had cat problems, and in fact, my original left sided cat had to be replaced about 2 years ago when it went bad.

I think this one did throw a cat efficiency code on 1 or 2 occasions, but only after running at high rpms, and not consistently. In retrospect, my service adviser mentioned that if they have another car come in with a similar problem, the cats will probably be one of the first things they look at, rather than the last.

Edited January 4, 2011 by KS-CS

[RFM]

wvicary, Faulty cats are more common over here, partial melted and broke as well, and have only two years warranty :angry: . In all cases of engine codes (PIWIS), misfires, etc. we did a supplementary quick cat test as following, four exhaust gas test HC - CO -CO² - O² on both banks, using the left - right difference values to detect anomaly's, followed by a cat temp test with a digital temp tester, the output side should be 50°C hotter than the input if the cat is still in good shape. Damage to the cat should be already, serious before a specific code appears.

[coleta]

RFM,

Could you share with us:

1. what normal HC,CO,CO2,O2 reading are?

2. are they checked before or after the cats?

3. under what conditions? at idle? 3000 rpm? or is it while driving under load?

4. what readings with HC, CO,CO2,O2 indicate bad cats?

And thanks for the temp difference info.

[wvicary]

I still don't understand the relationship between a failed convertor and the fault codes the poster was getting. A misfiring cylinder can easily damage the convertor and I have seen convertors melted to such a degree that the engine will stall after running a short time but never set fault codes for anything like this.

[RFM]

COLETA

1) HC 20 - 100 ppm / CO 0,01 - 0,03 / CO² 15% - 16% / O² 0,1

2) Exhaust tip

3) Hot engine, idle + 3.000 RPM with slightly varying values

4) Abnormal values may indicate cat problems when used together with a digital temp. gauge and PIWIS in "ACTUAL VALUES" mode. The specified values refers always to stock engines, DME and cats, and may vary depending on the generation of the used DME and pollution standards EURONORM 3 - 4 - or 5.

This simple verification process takes just 5 minutes longer than the usual procedure, it can be performed at the same time with the PIWIS and hot running engine, provides a quick and reliable diagnosis.

Of course, knowledge and experience are necessary to diagnose, because it is not just to read date from a sheet.

WVICARY

Indeed, normally the engine should trow misfire codes on the respective cylinder bank in first place, but well, we were finally not there and can only assume.;) :cheers:

[coleta]

Awesome stuff. Thanks