Hello,

Just picked up a stock, 997 '05 Carrera S with 40K miles. I believe the plugs are original and so are the tires. However, the following errors are present:

P0300 Random/multiple cylinder misfires detected
not present/intermittent/Freq 1 1425.2 hrs

P0301 Cylinder #1 misfire detected
not present/intermittent/Freq 1 1425.2 hrs

P0303 Cylinder #3 misfire detected
not present/intermittent/Freq 1 1425.2 hrs

Diagnostic performed at 1427.6 hrs.
Currently the hrs are 1431.2
NO CEL.

To start, I would like to think all spark plugs should be replaced and all coil packs? Will the CEL come on if the condition remains or is the threshold looking for consecutive cycles prior displaying the CEL? I do not know if fuel level was low when the errors were detected and if the previous owner was taking a corner when these misfires or non ignitions were logged? To me, the car seems to be running fine - not sure what to expect since this is my first Porsche. The issue is only with #1 and #3 at random times and not the entire bank. And the frequency is only 1. The previous owner stated he didn't feel anything at the time. I only have 4 hrs on the car - it is that new to me.

Any additional comments or insight is appreciated. Thanks in advance. This forum is a wealth of information.

 

Many post diagnostics. I've not seen cylinder misfire so you certainly should not expect this in the sense that "they all do it". You might suspect a fuel issue, would think it unusual for multiple coils to malfunction, but...? There are reports of motors failing to take gas properly for a brief instant, cause unknown and self correcting, but I don't know what if any codes that throws. If it worries you I would find a good independent shop, one that sees a lot of P's (ask around) and hope it is as minor as it seems. Or you could be optimistic and just drive it (my choice). I wouldn't just start changing plugs, etc, at 40K. It's not as if that stuff is cheap. Good luck.

 

Well if 0300 shows up, it's going to happen again. Are you saying there is no and has never been (since you've owned it) a CEL?

For misfires it'll Blink while it's happening.

One option is to hook the car up to a diagnostics unit and monitor for misfires while running the engine and spritzing it with water at the coil packs. When these coils fail it's usually due to cracking and water will accelerate the arcing. At the price of coils, I'd probably only replace as required unless you like spending money needlessly.

I wouldn't worry about plugs unless there is a good reason to change them or the tech doing the work is giving you a smoking price because he's 'already in there'.

 

Also, if there's a fueling issue, it'll usually result in O2 sensors picking up a bank running lean.

 

Thanks. I'm only into the car 4 hrs. I understand the CEL has never been on. I'll run another dianostic next week to see if the the incidents increase. Again the car is new to me and this is the only thing that stands out. I'll continue to learn more about this vehicle as I put more miles on it.