19 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHMaybe I am crazy...knocking/vibration '03 996
Leading reported evidence
Replace on schedule and are not due
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.
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
(Other 996 Turbo owners have found the coils bad in fewer miles so I am towards the upper end of coil life expectancy I think.) The plugs have been replaced on schedule and are not due.
Inspect from top(spark plug holes) and bottom(drop sump/pan)
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
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.
Suggestion
The only way I'd risk it is with an invasive PPI where you can inspect from top(spark plug holes) and bottom(drop sump/pan) to see if there are any metal debris and scoring outside of initially pulling the error codes.
Leading evidence: 'Replace on schedule and are not due' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'coils are "bad"' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Inspect from top(spark plug holes) and bottom(drop sump/pan)' (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
Idle was rough and ran like it was not firing on all cylinders.
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
However, I as noted at the outset, you by your own words are a bit of a gambler regarding used cars.
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
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 suspect 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.
Suspected cause
I believe that if the engine behavior was due to plugs/coils these would have been addressed.
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
Inspect from top(spark plug holes) and bottom(drop sump/pan)
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
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.
Suggestion
The only way I'd risk it is with an invasive PPI where you can inspect from top(spark plug holes) and bottom(drop sump/pan) to see if there are any metal debris and scoring outside of initially pulling the error codes.
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
So, I am shopping for a 996 to replace my 986 S and came across a smoking deal on a '03 but when I went to fire it up the motor made a nasty loud knocking sound and shook the car.
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
(Other 996 Turbo owners have found the coils bad in fewer miles so I am towards the upper end of coil life expectancy I think.) The plugs have been replaced on schedule and are not due.
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
Unless you can get an extensive inspection done and feel ABSOLUTELY certain that it's not something much more ominous, "RUN" really is the correct advice.
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.
19 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: 20261027T044418Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
So, I am shopping for a 996 to replace my 986 S and came across a smoking deal on a '03 but when I went to fire it up the motor made a nasty loud knocking sound and shook the car. Idle was rough and ran like it was not firing on all cylinders. The dealer still told me to take it out for a test drive and the noise and rough running of the engine continued the whole time. I barely drove it as I was not comfortable treating a car like that.
Now the deal is borderline good enough that if the engine is done it will not be a huge issue, but it would be good on the flip side if was something non-catastrophic. The CEL is on, but not flashing.
I am just trying to do a bit of homework on what could be the issue before committing to a PPI or other further inspections that will cost me money. As the car is about 300 miles away from me, it is not overly convenient to get a PPI done or do further inspections on it myself. So I am hoping you guys might have some insight to help me decide to proceed or not.
I know most of you will likely tell me to run...but I don't mind projects and I like to keep what is otherwise a pristine car on the road.
Thanks,
Matthew
BEST case, it's misfiring because of some bad plugs or coils, or maybe a bad MAF + vacuum leak could result in extensive stumbling...
Unless you can get an extensive inspection done and feel ABSOLUTELY certain that it's not something much more ominous, "RUN" really is the correct advice.
There are countless 996's on the market - unless you're just dying for a project, there's no reason to settle for one that doesn't run properly. Without knowing the specifics about why this one counts as "pristine," all I can really say is that a pristine 996 doesn't run the way you describe this one running. Someone posted in another thread a 996 for under $10K that runs better than the one you're describing. While it's certainly not pristine, a respray costs less than an engine...
RUN, RUN, so far away! Obviously you have not done your homework on this forum. Doubtful it's something simple, and if its engine internals it's a minimum of 10K for a used engine and more like 15K plus.
The only way I'd risk it is with an invasive PPI where you can inspect from top(spark plug holes) and bottom(drop sump/pan) to see if there are any metal debris and scoring outside of initially pulling the error codes. What kind of price are we talking about?
Matthew,
There are lots of "smoking deals" on 996's out there. Why not keep looking until you find one that doesn't have what is likely a big $ issue?
Just my $0.02 worth.
Even then it's not like there are a shortage of these cars at good prices. So maybe I'd do this if it was a really really awesome price, but, it'd be just as easy to find another one to buy.
I agree hence why I was curious on the price. If it was 4 digits and and someone was mechanically inclined, I'd say it could be a worthwhile risk after my aformentioned initial checkup.
Like Alpy et al have said, some additional info on price really would be helpful. A 996 with a "done" engine has the potential to cost you $10-$20K (or worse!) more, so this deal must be spectacular for you to even be considering it.
The flashing light means that the catalytic converters are at risk - a non-flashing light is no guarantee of less costly repairs...
I completely disagree with you. And those miles are not excessive. It's a well maintained car. I would rather have a high mileage well maintained car that's over 12 years old vs a low mileage car rotting in the garage anyway.
You should research what people are paying for 1999-2001 1st generation C2s and then compare back to this price.
It's a good deal for a C4S with good maintenance and right mods.
Thanks for the responses, and perhaps 996 are plentiful in the US, but up here in Canada for what I am looking for I have maybe 4-5 coupe to look at within 300 miles of my place...I know I just drove 600 miles yesterday to look at the closest 996s available under $25k. I typically include the US in my searches, but with our dollar the way it is...it just doesn't make sense these days.
To answer some questions, I think I could get it for around $15k CDN...now maybe not a smoking deal, but if the engine would be repairable for under $5k then great deal. If the engine is about to implode and will need to be replaced then no longer a good deal. I am a bit of a gambler with my used car buys. I am in year five of owning a '02 Boxster S that had all the red flags on why not to buy it. 15,000 miles later it has only cost me oil changes. The car now has over 120,000 miles and just keeps going. I am simply tired of driving a convertible, so looking for my next project.
I did do a quick search here before posting as that is what I usually do...I only post if I can't find an answer. Perhaps my keywords are no accurate enough but nothing came close to describing this issue. So I posted hoping there might be a "it is likely this issue..." response. But alas, things are never that simple.
Thanks again...
With our dollar the way it is, that $19,999 car becomes a $26,000 car then I hit the border and I pay 6% tariff on the CDN value which brings it up to $27,500 and then I have to pay 13% tax, pay for a flight to the West Coast...I am closer to the other side of the country. All that to say that is still a good deal compared to local options but it starts to become too rich for me at this time. A couple of years ago when our dollar was on par it would have been a no brainer. That is why my Boxster is a LA car and most of my friends drive US cars. Now, from my understanding, all the cars are leaving Canada for the US.
You are a bit of a gambler with used cars and appear to have had good luck.
So, take a gamble.
But let me say this. With the engine acting up you were unable to really test drive the car. The car might have other issues, like shifting or road feel or something that could be the tip of an expensive iceberg to address.
Next, and this should have been first, I'm always put off by a car for sale that has obvious issues. I believe that if the engine behavior was due to plugs/coils these would have been addressed. That the car was offered for sale with this behavior strongly suggests the root cause is something deeper.
This to me makes the car a lousy gamble.
You can revisit the car and with an OBD2 code reader read the active (and pending) codes. Post for comment.
However, even if the codes point to misfires the engine's knocking and poor running are very bright red flags to me. Case in point: My 996 Turbo's CEL came on the other day shortly after starting th engine. The engine was idling ok, a bit rough, but that is characteristic of the 996 Turbo engine. I was pressed for time and drove the car to the office 30 miles and home again with the CEL on. I never had the time to read the codes at the office. But the engine was running just fine.
This AM I read the codes: P0300, P0303 and P0306. The same codes that appeared under almost exactly the same circumstances a few weeks ago.
Now I strongly suspect the coils are "bad". They are original and have around 133K miles on them. (Other 996 Turbo owners have found the coils bad in fewer miles so I am towards the upper end of coil life expectancy I think.) The plugs have been replaced on schedule and are not due.
My point in all this is that given the extraordinary bad behavior the engine in the car you looked at manifested likely there is something more than just "coils" wrong with the engine. Even if you just get misfire error codes I would still be very very leery of the car.
However, I as noted at the outset, you by your own words are a bit of a gambler regarding used cars.
So take a gamble. Personally I'd give the car a wide miss.
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