20 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHCode P0300 Random misfire detected +P0301 and P0306
Reported or suspected cause
found
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
Reported fixes
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that report identifying a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Code P0300 Random misfire detected +P0301 and P0306
Read full discussion summary
Leading evidence: 'found' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'found' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Check engine....drive' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that report identifying a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Reported cause · Original poster
Also, I find it little odd that the problem is happening on cylinder 1 and 6 that are on different sides.
Code P0300 Random misfire detected +P0301 and P0306
nightmare (
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
Reported fixes
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that report identifying a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Code P0300 Random misfire detected +P0301 and P0306
Replace 6 coils, and perform the 60k service
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
We ended up changing all 6 coils, and perform the 60K service.
Code P0300 Random misfire detected +P0301 and P0306
poorly constructed cam, bad quality control, etc
Suggestion or failed attempt
No successful repair reported for this finding.
0
Identified cause
1
Suspected cause
0
Reported fixes
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that suspect a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suspected cause · Original poster
Macster, regarding the cam, my mechanic thought that the problem was a poorly constructed cam, bad quality control, etc.
Code P0300 Random misfire detected +P0301 and P0306
related
No successful repair reported for this finding.
0
Identified cause
1
Suspected cause
0
Reported fixes
Read evidence and context
Discussions that suspect a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suspected cause
Well, with the plugs having some miles on them and the coils being probably original then that provides a ray of hope the misfire cause is related to plugs/coils.
Code P0300 Random misfire detected +P0301 and P0306
Coverage and how to read this overview
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
20 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261026T142254Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Driving 03 CS4 home from a track event this evening, the check engine light came on and the engine felt jerky and rough, especially when driving over 50mph . I got the car towed home.
Codes were;
P3000 Random Misfire Detected
P0301 Cylinder 1 misfire
P0306 Cylinder 6 misfire
The car has little over 55k miles. Any ideas what is causing these codes?
I appreciate your help
A CEL with the engine running poorly is generally not a time to take up DIY engine diagnostics.
Without knowing the history of the car all I can offer is the obvious: Coils/plugs.
But there are other causes too. In one case a bad MAF was triggering misfires and just one bank too.
Unless you are prepared to get your hands dirty my advice is to tow the car to a qualified Porsche shop (dealer/indy) and have the misfires looked into.
Thank you for your reply Macster. I wasn't planning on doing the work myself, however just educate myself on the possibilities. The car has little over 55k miles. Last CEL problem turned out to be a nightmare (
https://rennlist.com/forums/996-foru...-opinions.html
)
One think I forgot to mention is that the CEL was flashing. Also, I find it little odd that the problem is happening on cylinder 1 and 6 that are on different sides. Any opinions on that?
About the only thing I can maybe take away from the misfires on both cylinders 1 and 6 is is that the problem might be a common failure, common to both banks. Maybe.
I did read the link you provided and I then recalled the what you went through before. What a nightmare. But the cause of the problem was found. However, I do not want to dump more gloom on you in your situation but I just watched that video for the first time and I was left wondering why the cam developed that flow problem? Was the cam bad or did something make it go bad?
Anyhow, IIRC the plugs and coils are I guess new, or new enough that they can be moved down the list of possible things to consider, though I will say that marginal coil connections at the wiring harness has been known to cause misfire grief.
Since you are not going to tackle this yourself time to get the car to your favorite shop and get the car on the road to good health.
Maybe.
Maybe not.
What would you say about all the car owners who have reported a flashing CEL without having just left the track, some have never been to the track? It's their imagination?
Come give the poor guy a break. His engine's sick, possibly seriously sick, though I hope I'm seriously wrong, and it turns out to be something relatively minor.
Mac, I know your trying to think positive but flashing CEL w/misfire on both banks leaving track? I think we know where this is going. I hope hes not still running the engine. I agree he needs some pro help.
Macster, regarding the cam, my mechanic thought that the problem was a poorly constructed cam, bad quality control, etc. The cam ended up collapsing, which eventually led to the blockage.
The 60k service hasn't been performed yet, it was to be done this summer. So the spark plugs are relatively old (changed at the 30k service). As far as the coils, I think they the original.
KrazyK, can you share with us what you think the problem is. You keep mentioning the track, but I know that there are lot of people on this forum who track their Porsches, and haven't had this problem.
I am hoping to keep the focus of this thread about the mechanical problem, but I can tell you that my track event wasn't exactly a race, but a PCA DE event. Porsches are built to be performance driving cars, and they can withstand some spirited driving, don't you think?
It is very possible that driving on the track could have contributed to the problem, but the CEL came on at ~ 20 miles after I left the track, on the highway, where my avg speed was probably higher than the track. (It was a slow track!)
Well, with the plugs having some miles on them and the coils being probably original then that provides a ray of hope the misfire cause is related to plugs/coils.
Given what ultimately turned out to be the cause of your engine troubles a while back I was not looking to get pulled into a quagmire of trying to offer any help regarding misfires causes.
Anyhow, I'm thinking -- hoping anyhow -- the track time extracted the remaining life from the plugs and coils. But your trusted mechanic will have to make this determination.
I'd look at the coils and plugs, and then the AOS. If the AOS is failing and blowing oil into the intake you'll get misfires and rough running. Many track rats run oil slightly below full to avoid pulling extra oil into the air stream.
Regarding Krazy's comments: "E' meglio vivere un giorno da leone che 100 anni da pecora" (it is better to live one day as a lion than 100 years as a lamb).
Flashing CEL is not a good sign, the misfire counts in the measured time interval kept increasing, so you were likely running on 4 cylinders. Hopefully it's just bad coils - any issues with oil pressure?
Clue of what? Dropped coils? Bad Maf? Scored cylinders? Internal damage? Electrical problems due to all the vibration? Exactly what does a track even clue you into?
Low oil pressure on the gauge after a track event is a clue; cel tripped by misfire counter can be a million things, regardless of where the car has been.
I had a recent CEL (not flashing, though) with codes:
P3000 Random Misfire Detected
P0305 Cylinder 5 misfire
It seems to have been caused by a failed regeneration valve. $100 part, ten minutes and no CEL.
996 110 129 53 Regeneration Valve from Throttle Body for Fuel Vapor System
I had the typical prior symptoms like car was difficult to start after fueling, etc... A regeneration valve failure can also cause the car to throw O2 sensor codes as well.
A flashing CEL means "DO NOT DRIVE" by the way... catastrophic failure is right around the corner if you do.
Hope this helps.
Best,
TomF
The car is in the shop, and the mechanic seems to think it's a coil issue too. I'll give an update.
This is a great quote/proverb. I will remember this. Thanks Ubermensch!
I didn't check the oil pressure before the CEL, but after the CEL I remember glancing at the oil pressure, and it may have been little lower than usual, but not very low.
Car is back home. The problem was.... bad coil ....Mechanic said it was one bad coil. We ended up changing all 6 coils, and perform the 60K service.
He told me that he sees this problem at least once a week. He's confident that track event didn't play any role in accelerating the process. He sees coils go bad in many non tracked cars.
Thanks to everyone who posted to this thread, sharing the knowledge and experience and for being positive.
I guess now I have some more days to live like a lion this summer
(thanks Ubermensch)
Glad things worked out for you Sam. I had to replace all six of my coils at 60k miles as well, before I ever tracked the car. Now, 60k miles later, and many, many track days later...they're still fine. Maybe track days improve coil life? Kidding...But seriously, enjoy your car for all it's worth. Tracking cars definitely puts them under more stress and you will have more repairs to keep up with. Frankly, I think of it as weeding out the weak links...One day my engine may blow (whether I track or not), but I'll never regret all the fun I've had how much better driver I am today than when I started.
This is a source reference. Confirm exact model applicability in the original material.
