15 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
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YOUR RESEARCHPlethora of Check Engine Codes
Reported repair
Combined work: Replace cap and all the misfire codes were gone + Replace coil caps
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1
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0
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Reported fix · Original poster
I then swapped the coil caps on cylinders 4 and 5 and sure enough the misfire moved to cylinder 5. Replaced the cap and all the misfire codes were gone.
Leading evidence: 'Combined work: Replace cap and all the misfire codes were gone + Replace coil caps' (1 discussions report resolution; 0 report an unsuccessful attempt). Across 1 matching discussions, the most frequently mentioned possible cause is 'loose battery connection...oops' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Combined work: Replace cap and all the misfire codes were gone + Replace coil caps' (1 discussions). For that action, 1 discussions report a resolution and 0 report an unsuccessful attempt. The most frequently reported fix is 'Combined work: Replace cap and all the misfire codes were gone + Replace coil caps', supported by resolution reports in 1 discussions. These are forum reports and suggestions, not a confirmed diagnosis.
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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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Reported cause · Original poster
The erratic idle turned out to be a loose battery connection...oops.
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 · Original poster
I recently installed a 99 carrera 996 engine into my 99 boxster.
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 · Original poster
Replaced the cap and all the misfire codes were gone.
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
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Performed · outcome unconfirmed · Original poster
I then swapped the coil caps on cylinders 4 and 5 and sure enough the misfire moved to cylinder 5.
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
Combined work: Replace cap and all the misfire codes were gone + Replace coil caps
1
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that report a fix
1
1 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 fix · Original poster
I then swapped the coil caps on cylinders 4 and 5 and sure enough the misfire moved to cylinder 5. Replaced the cap and all the misfire codes were gone.
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
Combined work: Replace cap and all the misfire codes were gone + Replace coil caps
1
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that report a fix
1
1 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 fix · Original poster
I then swapped the coil caps on cylinders 4 and 5 and sure enough the misfire moved to cylinder 5. Replaced the cap and all the misfire codes were gone.
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.
15 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: 20261026T072535Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
I recently installed a 99 carrera 996 engine into my 99 boxster. So far I've been having some issues with a large number of check engine codes. I've listed them below. Any suggestions for areas to check that might be causing these? By the way, my dme is still the boxster program as I wanted to get these issues settled before reflashing but that shouldn't be causing codes.
About to get fault codes
moduleType = MotronicDME78
DTC Count = 9
Fault Number:P0300
Description:Porsche fault code 507 - Misfire detection
Repair Infomation
total)
DTC Count = 9
Fault Number:P0306
Description:Porsche fault code 509 - Misfire cylinder 6
DTC Count = 9
Fault Number:P0303
Description:Porsche fault code 512 - Misfire cylinder 3
DTC Count = 9
Fault Number:P1585
Description:Unknown DTC: 1585
DTC Count = 9
Fault Number:P0304
Description:Porsche fault code 511 - Misfire cylinder 4
DTC Count = 9
Fault Number:P1319
Description:Unknown DTC: 1319
DTC Count = 9
Fault Number:P1318
Description:Unknown DTC: 1318
DTC Count = 9
Fault Number:P1316
Description:Unknown DTC: 1316
DTC Count = 9
Fault Number:P1315
Description:Unknown DTC: 1315
Application closing at user request
Boxster Selected
Boxster Selected
Things to work with for diagnostics.
Is it always the same cylinders.
Have you combined boxer and 996 electronics control parts.
Old gas being used? Gotta have fresh gas since it does start going bad after a few to 6 months.
Try listing the swapped in parts and where did the engine come from since the engine might of been that way from the start.
Gas and oil are fresh. Gas in the tank was 18 months old so I pumped it all out and added 4 gallons of fresh premium. The oil is brand new mobil 0w-40. It is always the same cylinders. All the electronics came from the boxster. Motor came from another member on here.
Looks like all of the 1300 level codes are also misfire related. Could that be vacuum related? I'm gonna try swapping spark plug caps, and if that doesn't do anything then I'll try replacing the injector o-rings and manifold gaskets.
I'm using the fuel rails from the 911 motor which was sitting dry. You still think I should remove it and try cleaning it out with some carb cleaner or something?
Turns out the number 3 spark plug was cracked. Swapped the plug and it runs like a completely different motor. I still get a misfire on cylinder 4 under real hard acceleration so I'm gonna buy a whole new set of plugs and drop them in. I also think the idle stabilizer may be bad bc sometimes the idle fluctuates around 500 rpms. And the valve makes weird buzzing noises after the car is off till you tap it and then it will stop.
Ok, I'll give that a try. Here's one of the codes it started throwing:
DTC Count = 5
Fault Number:P0506
Description:Porsche fault code 32 - Idle control at stop
So I'd say its safe to assume that is probably the culprit.
The other four codes that are showing up now are misfire on cylinder 4 and a couple other generic misfire related codes to that cylinder. So I'm definitely making progress.
In case anyone else runs into these same problems, here's what the causes were. Cylinder 3 had a cracked spark plug. Replacing that cleared up the misfires on cylinders 3 and 6. I then swapped the coil caps on cylinders 4 and 5 and sure enough the misfire moved to cylinder 5. Replaced the cap and all the misfire codes were gone. The erratic idle turned out to be a loose battery connection...oops. Now I'm getting an air bag code 48 which looks like the passenger seat belt buckle. So tomorrow I'll check that with an ohm meter to see if it's faulty.
