oddjob142

So, this has been quite an adventure. If anyone can provide any input, I would appreciate it. I purchased a 997 turbo with an evt700 kit on the car. Very soon afterwards, there was CEL and it was misfiring code on cylinder 3 and 4. The plugs and coils hadn't been replaced for quite some time and so we went ahead and changed out the plugs and coils.

The headers were cracked and we got new headers in and replaced them as well. The cats had a little unraveling in the center but overall looked find. Everything went back on and we started the car. We had the CEL still on. P0300 and P0304. Misfiring and cylinder 4. When we actually went in to look at the values and the etc, cylinder 4 looked find. There were no misfirings in the log, but the values were up and down on cylinder 1 and 5...it would vary...sometimes -48, 0, and 3-400. But there would be NO misfires in the log. Cylinder 6 maintained 1400-1800 values BUT there were no misfiring documented. We tried to reset the codes, but for some reason, it would not let us reset the codes.

Our gameplan is that we are going to try another diagnostic tool Monday to reset the code, if that doesn't work, we are going to replace the two coils AGAIN. If that doesn't work, it may be the ECU? If anyone has any ideas or has seen this before, please let me know. I am thinking it is the diagnostic tool and that the codes are from the old CEL and that maybe cylinder 6 coil was bad from manufacturer. Fingers crossed....

oddjob142

Also forgot to mention, the care sounds great and there is no knocking. Revs fine and doesn't sound like it's misfiring.

TT Surgeon

Do you have a pic of the cat 'unravelling', that could be the issue.

oddjob142

I don't have a picture of the cats, but it just looks like the center was a little deformed / pushed in, the size of a pencil tip. I was told from evolution that the cel light for the 2nd o2 sensor was very likely eliminated with the tune(b/c many people run cat bypass or straight pipes), but they are confirming that Monday.

TT Surgeon

A bad cat usually throws a 2099 or 304, if the cat element is damaged at all, it's shot and must be replaced. You don't want that fragmenting and getting sucked into the turbo $$.

oddjob142

Would it still show a high value on cylinder 6 w/ a bad cat? I sent the cats to fabspeed b/c they were considering warrantying them, but the ended up not covering it. They said I should be able to run them for a bit before I needed to purchase new ones or go with cat bypass. I guess I need to get with EVOMS monday and confirm if my ecu had the second o2 sensor overrided.

oddjob142

The CEL just needed to be reset. The diagnostic tool they were using was acting up and when they plugged in another, they were able to clear the codes that were showing PRIOR to changing the coils and plugs. After a drive cycle, no codes or values. Thanks for your help....