5 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCH911 996 C4 miss fire
Reported or suspected cause
dirt in the valve lifter
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.
Leading evidence: 'dirt in the valve lifter' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'dirt in the valve lifter' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Check damage and blow out oil passages' (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 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
The dealer has come back saying it is a faulty catalytic converter, now replaced along with the pre and post lamba probes.
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
Replaced the Cat and lamba (oxygen) sensors on that side of the engine, 911 back on the road and running better than ever, very smooth through the entire rev range, just a dented wallet!
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
Oxygen sensors and vario cam solenoids have been swapped over, CEL still registers same fault on cylinders 1 and 3
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 have had a major service, replaced plugs and coil packs.
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
Replaced the Cat and lamba (oxygen) sensors on that side of the engine, 911 back on the road and running better than ever, very smooth through the entire rev range, just a dented wallet!
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.
Suggestion · Original poster
Besides the list of all the normal system tests (which the engine pasted) the garage use a "borescope" to examine the exhaust’s including both catalytic convertors and found the left hand side ones' honeycomb was deformed and detached from the casing, right hand side cat not showing any signs of adverse ware.
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.
5 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Porsche Club GB: 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: 20261027T003124Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
We have had a major service, replaced plugs and coil packs. CEL still comes on over 5000 RPM.
The air intake and exhaust systems have been tested for gas tight, OK.
Coil packs have been moved to different cylinders, CEL still registers same fault on cylinders 1 and 3
Oxygen sensors and vario cam solenoids have been swapped over, CEL still registers same fault on cylinders 1 and 3
Has anyone had similar problem and knows of any possible fix?
Any help appreciated
Bob
Hello Richard, Many thanks for the reply. Injectors and fuel pressure all checked out - OK as are the cylinder pressures The error codes are: - P0300 & P0303 and sometimes P0301 The Garage tells me they are going to check for blockages in the left exhaust next (CAT or baffles) Any ideas appreciated Bob
Below are extracts from the diagnostic sheets. If you would like a full copy, drop me an email:
Function: To detect misfiring, the drop in engine speed which results when there is a partial lack of combustion at one or more cylinders is evaluated. A distinction is made between emission relevant misfiring after start-up, emission relevant misfiring during the journey and misfiring which is damaging to the TWC. (See fault text table on page P - 3). The engine speed is measured with an inductive sensor that is located above the ring gear on the flywheel. The ring gear is divided into three segments. For detection, the time between two segments is measured and the difference calculated. This difference is corrected by a mean value that is developed over several segments, to compensate for engine speed fluctuations caused by driving conditions. If the corrected value is above a specified threshold value which is dependent on engine speed and engine load, a misfire is detected. (See also Misfire detection description on pages B - 1 to B - 2). DTC No. - Fault conditions P0300 - Misfiring in several cylinders P0301 - Misfiring, cylinder 1 P0302 - Misfiring, cylinder 2 P0303 - Misfiring, cylinder 3 P0304 - Misfiring, cylinder 4 P0305 - Misfiring, cylinder 5 P0306 - Misfiring, cylinder 6 Fault area: – Mechanical causes – Fault in ignition system – Fault in injection system Combustion miss – Mixture too rich – Mixture too lean Possible mechanical causes of faults: Valve lifter chattering. This is caused by dirt in the valve lifter. When the Check Engine MIL lights up, a chattering valve lifter may also occur for a certain time. The DME control module registers (sporadic) misfiring at one or more cylinders. The mixture adaptation values are normal. Remedy 1. Remove lifter bores, check for damage and blow out oil passages. 2. Replace all valve lifters (engine installed). 3. During the test drive, listen for valve lifter noises.
The dealer has come back saying it is a faulty catalytic converter, now replaced along with the pre and post lamba probes. Besides the list of all the normal system tests (which the engine pasted) the garage use a "borescope" to examine the exhaust’s including both catalytic convertors and found the left hand side ones' honeycomb was deformed and detached from the casing, right hand side cat not showing any signs of adverse ware. Probably as a result of the faulty coil packs which caused the misfire and in turn allowed unburnt fuel into the exhaust where it has ignited and burn away some of the cat and it's fixings which is causing a blockage in the exhaust system at higher rev's. Replaced the Cat and lamba (oxygen) sensors on that side of the engine, 911 back on the road and running better than ever, very smooth through the entire rev range, just a dented wallet! Also found this link which adds to the diagnosis: - http://forums.rennlist.com/rennforums/996-forum/696246-996-misfire-and-failing-catalytic-converter.html Thanks to the dealer who resolved the error for us. I can only hope this thread can help save someone else some of the expense......... Now lets have some sun shine and get the top down! Bob
This is a source reference. Confirm exact model applicability in the original material.
