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THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCH996: Engine Noise and CEL P0300, P0304, P0305, P0306
Reported or suspected cause
battery
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
Reported fixes
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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.
Discussions that report identifying a cause
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Reported cause
I had the exact same codes, part of the problem was a bad battery.
996: Engine Noise and CEL P0300, P0304, P0305, P0306
Read full discussion summary
Leading evidence: 'battery' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'battery' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Check alignment of the timing gears' (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 suspect a cause
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Suspected cause
I've seen cars with bad alternator manifest some engine behavior that to the uninitiated would have one suspect the engine was on its death bed.
996: Engine Noise and CEL P0300, P0304, P0305, P0306
mother of all bad gasoline
Suggestion or failed attempt
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Identified cause
1
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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.
Discussions that suspect a cause
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Suspected cause
Yeah I admit that would have to be some really bad/stale gasoline but there was a recent post (IIRC on another forum) about a Boxster owner who got some bad gasoline and it was the mother of all bad gasoline.
996: Engine Noise and CEL P0300, P0304, P0305, P0306
Check alignment of the timing gears
Suggestion or failed attempt
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
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Suggestion
The first thing I would do is rotate by hand to TDC and pop out the cam plugs and check the alignment of the timing gears.
996: Engine Noise and CEL P0300, P0304, P0305, P0306
Check cam timing
Suggestion or failed attempt
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Suggestion
Yea, you need to know a lot more than that, I suggest you download a shop manual and read up on checking the cam timing on a 3 chain m96 engine.
996: Engine Noise and CEL P0300, P0304, P0305, P0306
mother of all bad gasoline
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.
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Suspected cause
Yeah I admit that would have to be some really bad/stale gasoline but there was a recent post (IIRC on another forum) about a Boxster owner who got some bad gasoline and it was the mother of all bad gasoline.
996: Engine Noise and CEL P0300, P0304, P0305, P0306
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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.
29 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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Generation: 20261026T124918Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Hello, I'm new to the forum here. I started up my 996 today and had a really rough idle, followed by engine shutdown and CEL Codes: P0300, P0304, P0305, P0306. Also shot a quick video of what the engine sounds like when i start up the gas. I momentarily did press on the throttle to get a better sound of it. I'm thinking that the engine is totally done, and would need a rebuild or a swap. Thoughts?
Also a reference to a great Porsche Mechanic in the Orange County / Los Angeles Area would be greatly appreciated
Link to Video
Vimeo
Misfires may NOT mean the engine is toast. 4-5&6 cylinders all on the same side might be a significant indication. I would stay on the electrical side of problems at this time. Hard to say from the sound of your recording as only half of your engine is firing. That will make it sound pretty funky. I would not run the car any more until further troubleshooting.
I hear low compression on at least 1 cylinder on tick-over. I would start with compression test followed by checking cam timing. Or even start with checking cam timing, then compression test and borescope for valve/piston contact..
I have a feeling the noise is the valves contacting the pistons from a failed IMS shaft/ gears slipped.
Would it not make sense in the case to pull the belt an rotate by hand to see if anything (metal to metal) is making contact before starting?
AJ, out of curiosity, what year is your car?
The first thing I would do is rotate by hand to TDC and pop out the cam plugs and check the alignment of the timing gears. I would not even attempt to start it again until cam timing is verified !!
I don't think a chain is broken, I think the gear has slipped on the IMS shaft, that's why it is recommended to have the gears pinned to the shaft whenever the IMS shaft is out of the engine.
I have actually just last week began thinking of a way to lock the gears to the shaft without having to disassemble the engine. The gears are just a press fit to the IMS shaft and is one of the failure modes that I have seen too many of.
There are some expandable internal collets that can exert 10k pounds+ holding force ( a tube/pipe expander) to lock the IMS tube to the gears, if the right size collet was machined, it could be inserted through the rear of the shaft with the IMSB removed, there would need to be three of them. I may pursue this idea, or maybe L&N would be interested in developing it, there may not be much of a market for such a product.
Yea, you need to know a lot more than that, I suggest you download a shop manual and read up on checking the cam timing on a 3 chain m96 engine. If you are not comfortable that you can do it, it's probably best to tow it to a trusted mechanic and have it done.
You are so right about this....my son's boxster had a new rebuilt engine where it slipped twice...first time we thought the chain jumped a gear tooth. So we retimed it....then it happened again. Engine was sent back to rebuilder who pinned the gear on IMS shaft. No problems since....so the question is, was ajvalles' engine rebuilt?
The engine sounds quite sick. But is the engine really on its last legs?
Can't say.
How long has it been since the car was last used? Was the car ok then? If the car has sat any length of time there's bad gasoline. Probably not bad when you filled up the car's tank but if the car has sat a while it can go off. Yeah I admit that would have to be some really bad/stale gasoline but there was a recent post (IIRC on another forum) about a Boxster owner who got some bad gasoline and it was the mother of all bad gasoline.
I've seen cars with bad alternator manifest some engine behavior that to the uninitiated would have one suspect the engine was on its death bed. It was just the engine and the engine electronics trying to operate in a low voltage/current situation.
If the car has sat a while beside the gasoline going stale mice can have been at the car. A very sick running engine is often the first clue.
There are a number of at least possible explanations for what you are hearing. Regardless, the engine is not going to get any better with more run time. My advice is to do not start/run the engine again.
I think you are on the right path trying to find someone qualified to check the engine out. A tech with experience will have seen this before and know what to do
The engine might prove to have a fatal problem but it doesn't have to have this. Let a good experienced tech help you find out what's really going on.
Lots of great shops in OC.
Haydon Bros Anaheim
Vision Lake Forest
Hergesheimer Lake Forest
Cape Auto Mission Viejo
LA
Callas Rennsport
Red LIne Service
Hoping for a simple electrical issue.
Sorry havent been posting. Everything was really wrong with this car - IMS - Camshaft broke in 2, we're in the finishing stages of doing a full rebuild.
