26 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHMisfire cylinders 1, 3, 5 car runs fine?
Leading reported evidence
Replace engine
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
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0
Unsuccessful attempts
1
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Performed · outcome unconfirmed
However, I have to note after the O2 sensors were replaced the engine ran a bit better and after the plugs and coils were replaced the engine ran a bit better.
Leading evidence: 'Replace engine' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check long term fuel trims as well' (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.
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Performed · outcome unconfirmed
However, I have to note after the O2 sensors were replaced the engine ran a bit better and after the plugs and coils were replaced the engine ran a bit better.
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.
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Replace several times and never noticed any improvement
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.
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Performed · outcome unconfirmed
I've had the plugs changed several times and never noticed any improvement from the engine so I attribute the improvement to the coils.
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.
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0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
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Performed · outcome unconfirmed
However, I have to note after the O2 sensors were replaced the engine ran a bit better and after the plugs and coils were replaced the engine ran a bit better.
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
However, I have to note after the O2 sensors were replaced the engine ran a bit better and after the plugs and coils were replaced the engine ran a bit better.
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
However, I have to note after the O2 sensors were replaced the engine ran a bit better and after the plugs and coils were replaced the engine ran a bit better.
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
However, I have to note after the O2 sensors were replaced the engine ran a bit better and after the plugs and coils were replaced the engine ran a bit better.
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.
26 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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3 acknowledgements have no verified action link; they do not establish a repair result.
Guys,
I have a 2004 Anniversary 996 with 65K miles. New coils and plugs 10K ago.
Lately every 20 or 30 engine starts I get a CEL.
There are no hiccups or any other indication of issues, the car runs great.
The Durametric says Misfire - cylinders 1, 3, and 5 each time. This has happened three times now.
The car is driven three day per week and it gets a decent work out.
Are there any systems that involve these specific cylinders?
I cant figure out why the misfire codes are the same each time.
Any thoughts?
Thanks in advance, Paul
Cylinders on M96 are numbered sequentially, with 1-2-3 on one bank and 4-5-6 on the other - so the misfires are happening on both banks.
Any chance it's something easy, like bad fuel from a crappy gas station every so often?
Firing order, I think, is 1-6-2-4-3-5; if it was a fuel pressure issue, it seems strange that 2,4,6 are not logging any misfires.
Minimal chance of bad Chevron Super, however I am probably on the same tank of gas as when this issue started, so something to think about.
Car lives in typical SoCal weather
How much fuel is left? If not much (since you're on the same tank and drive the car often), can you pump the last couple gallons out and replace it with fresh?
Have you tried to watch the misfire counters in Durametric
in real-time
and see if you have misfires on all cylinders? What are your cam deviations, FRA and RKAT values on both banks? What's the MAF value in voltage when the car is idling with engine fully warmed up?
I haven't tried this.
Like I said, the code only shows up maybe once a month after say 30 engine start and drives (400 miles total). Once I clear the codes, it go's away for another month or so.
So (and maybe I'm wrong here) but I figure I wont be lucky enough to encounter a misfire at the time I'm plugged in?
You are reading too much into the specific misfire codes. You have misfires but maybe only #3 (or #5) and the other misfire codes are sympathetic to the first.
Second possibility, one cylinder's spark charge is misbehaving so badly that it affects the follow on spark to the next cylinder.
Coils, plugs and then compression to figure it out. You can swap good coils for 3, 5 and 1 or buy new.
You might find this of some value.
Been dealing with the occasional cold misfire on cylinders 3 and 6 of my 996 Turbo. (P0303, P0306 and P0300.)
I had new O2 sensors installed, the installation triggered by a CEL with a sensor error code. Then more recently I had new plugs and coils installed.
Didn't cure the misfires.
However, I have to note after the O2 sensors were replaced the engine ran a bit better and after the plugs and coils were replaced the engine ran a bit better. I've had the plugs changed several times and never noticed any improvement from the engine so I attribute the improvement to the coils.
But while the above helped the engine run better as I said above the cold misfires persisted.
Tech offered the opinion some injectors were dirty (or "lazy", sticking a bit) and even gave me a bottle of Swepco fuel system cleaner. I ran this through the fuel tank and the Swepco didn't help.
But I didn't give up. I then ran a bottle of Techron through the fuel tank. That didn't help. But I ran a 2nd bottle right after the 1st. That didn't help either. The misfires still happen.
The engine never misfires at any other time other than just a few moments after cold start. The engine does run/idle a bit rougher than usual cause often I'm thinking "the engine sounds like it is running a bit rough" only to have the CEL come on and sure enough every time with the same misfire codes the same 2 cylinders.
I have found I can avoid the cold misfires by not letting the engine idle after a cold start. So now my cold start involves getting everything ready: seat belt on; hook up my NAV and radar detector and put them in their holders; then I start the engine.
After just a moment or two with everything looking ok I back the car out from the carport and hit the road of course being easy on the engine until it is fully up to temperature.
The engine runs fine otherwise, delivers the same gas mileage as it ever has, doesn't use any more (or less) oil, and gives no signs of anything amiss (so to speak).
I am not sure what to do.
However, the car is due for a 150K mile service in under 1500 miles so when I take the car in for this I'll touch base with the tech and see what he recommends for the next step for I would like to find the cause of these misfires and eliminate them.
My point in all the above is you might be facing something similar. You can try Techron. Try 2 bottles, but use one at a time. I have to say when I switched from Shell gasoline to Chevron my Boxster engine after just a couple of tanks reacted favorably to the Chevron. Techron is a real deal in my experience.
'course, the Turbo engine didn't really show any improvement with the switch to Chevron but I just assumed the Turbo engine was a cleaner running engine. And it very well could be.
So if you want, if you haven't a better idea, try the Techron. I arranged to use it just before an oil/filter service as Techron can increase oil contamination and the last thing these engines need is more contamination.
Macster, I reread all 14 paragraphs, and for the life of me I don't understand where the advice is that OP may find of value...
"I tried two bottles of Techron to fix my misfires. It didn't help and I don't know what's going on. You should try it."
Yes, this seems dickish; but I always seem dickish...what did I miss?
"The car is driven three day per week and it gets a decent work out."
"
Lately every 20 or 30 engine starts I get a CEL."
The 997 tank holds 16.6 gallons
So how does your car get a "decent workout" from 20-30 engine starts over a month on the same tank of gas?
I must be missing something in this thread, all I see is a car driven in must be extremely brief drives on the same tank of gas, wouldn't it be simple to go for a long drive with a fresh tank of gas from another chevron?
Before you go and do coils, plugs, compression....
Again, I am missing something right
Again, I am probably missing a salient point
This is a source reference. Confirm exact model applicability in the original material.
