6 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHMystery cylinder 4 misfire with code P1316
Reported repair
Combined work: Replace valve springs + Run without issue - no more cel or misfires
Reported resolution
1
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 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
Replaced both valve springs on cylinder 1 He put everything back together and it was running without issue - no more CEL or misfires, but still with the slight vibration every few seconds at idle.
Leading evidence: 'Combined work: Replace valve springs + Run without issue - no more cel or misfires' (1 discussions report resolution; 0 report an unsuccessful attempt). Across 1 matching discussions, the most frequently mentioned possible cause is 'fueling issue' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Combined work: Replace valve springs + Run without issue - no more cel or misfires' (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 valve springs + Run without issue - no more cel or misfires', supported by resolution reports in 1 discussions. 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 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
He also checked the cam deviations, which were not great given their mileage (Bank 1 @ 5 degrees and Bank 2 @ -6 degrees) In total, he ended up doing the following:
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
Coils and plugs were replaced with engine rebuild with less than 3k miles on them, but he swapped the coil to test it just in case.
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.
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
Discussions that contain suggestions
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
Coils and plugs were replaced with engine rebuild with less than 3k miles on them, but he swapped the coil to test it just in case.
It's going back to the shop and the mechanic is thinking about replacing the coil because the ones I used with the rebuild were aftermarket, not Porsche genuine parts.
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 valve springs + Run without issue - no more cel or misfires
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
Replaced both valve springs on cylinder 1 He put everything back together and it was running without issue - no more CEL or misfires, but still with the slight vibration every few seconds at idle.
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
He also checked the cam deviations, which were not great given their mileage (Bank 1 @ 5 degrees and Bank 2 @ -6 degrees) In total, he ended up doing the following:
It's going back to the shop and the mechanic is thinking about replacing the coil because the ones I used with the rebuild were aftermarket, not Porsche genuine parts.
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 valve springs + Run without issue - no more cel or misfires
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
Replaced both valve springs on cylinder 1 He put everything back together and it was running without issue - no more CEL or misfires, but still with the slight vibration every few seconds at idle.
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.
6 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: 20261026T024951Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
My '99 Coupe 6MT with ~70k miles had a slight periodic vibration at idle (every couple of seconds). The car was running fine in every other way, but I wanted to make sure it was in a great state of tune, as I had it rebuilt with a factory small block the previous year. I noticed that the fuel trims were a bit off on one cylinder bank, and based on advice from RL, I did the following:
Replaced the MAF sensor
Replaced primary O2 sensors
That didn't help the vibration or fuel trim. Based on advice from here again, I suspected either a vacuum leak or fuel injector. Both are out of my comfort zone, so I sent the car back to my mechanic who had done the rebuild. Using a smoke tester, he found vacuum leaks in a crack in the oil filler tube and at the intake resonance valve. It seemed like we had found the culprit. Decided to replace those parts and put in new injectors, as recommended by FSI/LN for cars that had experienced bore scoring.
However, while the mechanic was moving the car at the garage, it started misfiring with code P0301 "Misfire Cylinder 1". Coils and plugs were replaced with engine rebuild with less than 3k miles on them, but he swapped the coil to test it just in case. That didn't help. So, he pulled the plug out and found it fouled with fuel. At this point, he dug further into the head, which had been refurbished with the engine rebuild. He found what he suspected was a weak intake valve spring on the cylinder. He also checked the cam deviations, which were not great given their mileage (Bank 1 @ 5 degrees and Bank 2 @ -6 degrees) In total, he ended up doing the following:
Replaced the oil filler tube and intake resonance valve to address vacuum leaks
Replaced the fuel injectors
Replaced both valve springs on cylinder 1
He put everything back together and it was running without issue - no more CEL or misfires, but still with the slight vibration every few seconds at idle. I took the car back and drove it ~100 miles without issue. But a couple days later, when I started it up, it would run very rough and the CEL light came on. My scanner indicated P1316 "Cylinder 4 misfire".
It's going back to the shop and the mechanic is thinking about replacing the coil because the ones I used with the rebuild were aftermarket, not Porsche genuine parts. I would love for it to be as easy as a coil, but it given the other issues, this doesn't feel likely to be an ignition issue to me. More likely a fueling issue, but I'm no expert.
What else should I be asking the mechanic to check here?
I replaced the pads when the engine was rebuilt with the factory short block. Some googling says it could be a variocam actuator issue. Does anyone know more about that?
about 10 in depth threads in the last 6 month about it. Try searching my username. A good scanner can read the actual cam angle and u need to read that to see if it moves at about 3200 rpm.
