nveeser

I've had my 997.2 for about 8mo. It's got ~77k miles at this point. There was an issue in October where this happened. I started cold, then the engine got rough right after I started driving. I restarted the car and it resolved itself. When I looked at the PIWIS it was the same error codes as now.

As of today it seems to stay. Looking at PIWIS I am getting P0175 O2 sensor is rich AND misfires on 4,5,6.

Is the O2 sensor complaining because the cylinders are misfiring or are the cylinders misfiring because the O2 sensor for bank 2 is off?
Is it possible I just have a bad / failing O2 sensor which is making the whole bank 2 misfire? If I recall modern O2 sensors have a relatively narrow operating temp. I understood that they have a heating element to get it there quickly.

Wondering if bank 2 is not (always) getting to temp as quickly as it should. Also I am in NorCal. It's never cold. Today it was almost 40 out (which is rare). I think it might have been similarly cold the last time this happened. Also it would be helpful to know if it's likely the before cat or after cat sensor?
What are some other issues that would affect all of bank 2 but nor bank 1?

Any suggestions on how to test the O2 sensor (short of just buying one and swapping it)?
Anyone want to throw out some insight?

Thank you in advance for insight

997ajk

Have you tried to reset the codes ? Do they come back right away or it takes time ?

If it comes back with 02 fault right away then it's faulty 02, if it comes with misfires on 4/5/6 you might have another issue (valve lift solenoid or camshaft position sensor)

Floyd540

Coil paks. They can drive you crazy as they almost never throw meaningful codes. If car starts fine and then after a few minutes runs rough then that is the problem. 997.2 coils start failing at 80,000+ miles. They are about $50 each. Do plugs at same time. I like your pic on the Dragon. I have the same one of my car. (2011 997.2) Been there, done that- dragon and coil paks.

MrMoose

With faults on all three cylinders, coil packs seems unlikely.

It could be a bad sensor causing the misfires, or the misfires causing a bad sensor reading. The O2 sensor isn't super cheap (maybe there are cheaper aftermarket ones, I didn't look very hard) but they do tend to wear out by ~100K miles and it's the easiest option, were it me I might just start with that.

BHMav8r

Proly not applicable, but I hasd misfire issues that would manifest after a clutch stall.

Local indy couldnt seem to make any progress on it, then after I put in a new battery it vanished.

Think it had to do with the battery being disconnected for aa while.

Good luck and keep us posted.

nveeser

So I did reset the codes and it came back after a minute of idling - sigh

* Coil packs
Installing the Fister exhaust and changed the plugs. The C6 coil pack has already been replaced.with OEM Beru
Since its on all 3 cylinders at once I am leaning away from a single coil pack

* Bank Specific
The main thought is to look at things that are bank specific. If the MAP was off, I suspect I would see misfires on both banks
If the a coil pack was off it would be a single cylinder.

* Vacuum leak
I asssume if there was a vacuum leak (like AOS hose broke...) then I would see a lean condition rather than rich?
Ie more air in the charge than the MAP was counting on and the fuel would be lean.

* valve lift solenoid or camshaft position sensor

Someone else mentioned this too - this seems like strong candidate as they are each bank specific and could cause issues with intake not letting in enough air.
Also the other post I read mentioned that the cam position sensor is irrelevant during the first minute of warmup - the car runs open loop.
once warm then sensor is used to adjust valves and timing?

This is easy enough to test as I can swap B1 and B2 on each of these and see if the problem moves to B1

Anyone know of any more direct tests of the solenoid or sensor?
Any suggestions on using PIWIS to validate any of this?

CAVU

How long ago was the Fister exhaust installed?

nveeser

Exhaust was installed in mid January. This has happened before, in October. Restarting the engine made the poor idle go away. Later I cleared the code and it didn't come back until now.

Not sure if they are related.

CAVU

Was the new exhaust inclusive of a new cat or is it a post cat exhaust?

MrMoose

It shouldn't matter. The upstream sensor (that controls the mixture) is ahead of the cat converter, and that's the one throwing the code.

If you remove the cat converter you'll get a catalyst efficiency low code, that's from the downstream sensor. That one is only there to monitor cat converter performance.

nveeser

Its the sharkwerks cross pipe and fister mufflers.
All the exhaust is after the CAT, everything before is basically untouched

CAVU

Got it. Looking for potential exhaust leak before the up stream O2 sensor -> leads to a the sensor measuring lean (false lean) and the ECU then calling for more fuel on that side.

nveeser

I like that theory - oddly I am also getting a code P0175 on Bank 2 - O2 sensor measuring things too rich.
Not sure if that's the before cat sensor though. Does it make sense that one would run lean and the other run rich?

Likely something I could see with the PIWIS if I knew exactly which values I was looking at.

CAVU

Since the bad behavior was an intermittent failure before the Fister install and appears to have gone to 100% failure, I do not think there is an exhaust leak, especially since nothing was touched at the head. It is possible that the gasket connecting the muffle pipe to the cat is faulty and that the post cat sensor is getting extra air and sensing a lean condition.

Also, what is your confidence level that the exhaust muffler is clear (no debris left over during install....far fetched I admit).

You will want to look at Fuel Trims and the values being reported by the two O2 sensors on that bank and compare to the other bank as a place to start.

nveeser

Interesting question - I am pretty confident that I didn't leave a rag or a but sitting inside the cat. And I probably would have heard it by now.

--
I pulled out the PIWIS again to try to diagnose.

The cam shaft deviations are 3.36 on bank 1 and 2.25 on bank 2
It seems odd they are different. But I don't know what the unit °KW is - (degree kurbel welle? - degrees from crankshaft)
And neither of them is 0. I assume that's measuing how far off the crankshaft that camshaft is. Doesn't seem broken...sigh.

----
The fuel trim mean value is 10.45 and -24.86 %
I assume this is the DME trying to pull down regulate fuel on Bank 2.

The actual lambda values hovers closer to 1.00 on bank 1 and bank 2 is closer to 0.88
FWIW its worse at idle than at 3k.

Eventually the nominal value for bank 2 moves up to 1.10 - I assume thats the DME adjust the set point.

Given that throttle reduces the problem makes it seem like a vacuum leak in the exhaust causing weird O2 readings.

Does the exhaust manifold, before the cat, runs at a vacuum or not, ie would a leak result in air being pulled in or pushed out?