15 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHPower Loss above 4000 RPM on 996 C4S
Leading reported evidence
Check codes and found p1120 and p1121
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
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Discussions that performed work without a confirmed outcome
1
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Leading evidence: 'Check codes and found p1120 and p1121' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check codes and found p1120 and p1121' (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.
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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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Performed · outcome unconfirmed · Original poster
I had just checked the oil level and it was normal.
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 have a generic scan tool that I've used over the years for other cars/trucks I've owned so that's why I ask.
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Suggestion · Original poster
Is there a special procedure for cleaning the e-gas throttle bodies?
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Suggestion
But first thing I would do on a 99C2 is to carefully remove the fuel filter without spilling/loosing any of the fuel contents, pour/empty into a clean glass jar to see if any rust/dirt, water, mud ect.
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Suggestion · Original poster
I run 91 or 92 octane, and try to use non-ethanol gas when I can but if not I add some Sta-Bil 360 ethanol treatment to try and mitigate the ethanol damage to the car.
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Suggestion
Install a manual pressure gauge with a very long line ( or use a high quality electric pressure gauge) ran out under the engine lid and over the top of the car (taped down) and onto the windshield..
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
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Generation: 20261027T140027Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Calling all Porsche 996 gurus out there. I had a strange thing happen on my way home yesterday and I'm hoping that someone can shed some light on it for me. I was on my commute home which takes me over a small mountain pass. I was at about 700ft above sea level and heading up the pass when I decided to pass a slow car in front of me. I down shifted and put the pedal all the way down and the car accelerated, but then once it got somewhere between 4000 and 5000rpm, it felt like someone pulled the e-brake. With the pedal all the way down, the car would not gain speed or RPMs. There were no CEL lights and no other symptoms other than a loss of acceleration and power. It was a warmer day, with temps in the mid 70's with sunny conditions and no wind. I tried it a couple more times and the same thing happened. I never got a warning light, and all the vitals on the car looked normal (temp, oil, voltage, etc.). This morning I decided to test it again. Since it was morning the temperature this time was in the mid 40's with no rain or wind. This time I was on a flat road and when I put the throttle down the car surge with power and the revs kept going and going. No hesitation and none of the symptoms of the day before. I was at about 500ft above sea level during the morning test. For more details the car is a 2003 C4S with no mods other than the Fister exhaust mods. It has the stock intake and a normal air filter (no K&N or cold intake). I had just checked the oil level and it was normal. I was not running the AC unit for either test. I run 91 or 92 octane, and try to use non-ethanol gas when I can but if not I add some Sta-Bil 360 ethanol treatment to try and mitigate the ethanol damage to the car. I had been driving the car every day for a couple weeks and there have been no other issues with it. It starts fine and idles fine with no hesitation or backfires or any other issues. Any thoughts as to what is happening with it? Thanks in advance for the help.
Some faults will set a "Pending Code" in the DME.
The Pending Code will wait for a "conformation" on the next drive cycle before it will set the dash CEL Warning.
If the Pending Code does not get a "confirmation" ( repete of the fault) in 20 drive cycles, it will be "auto-erased" from the system without ever having illuminated the CEL Warning.
Have the car checked for faults very soon.
Before jumping to conclusions, do an e-gas calibration. Key in ignition, turn the key to ON (not start), wait 60 seconds and turn the key off. There should be some whirring and clicking sounds from the engine bay. Do not touch the accelerator pedal while doing this.
Will any scan tool work or do I need a Porsche specific one? I have a generic scan tool that I've used over the years for other cars/trucks I've owned so that's why I ask.
Generic tools that work on OBDII comms will be able to pull codes to some degree. I have an $18 Bluetooth tool that does this. Other, more advanced tools might be a lot better.
I did this yesterday and the car seems to be behaving much better. Thanks for the idea. I'm going to try and duplicate the actions that initiated the power loss later today to see if things are truly working better.
The problem happened again on my commute home. I checked for codes and found P1120 and P1121. From what I’ve read it means the throttle body needs cleaning. Is there a special procedure for cleaning the e-gas throttle bodies?
Skip, found this comment by you on an earlier thread. At a recent DE event my 1999 C-2 began hesitating between 4000 and 5000 rpms. It occurred primarily on hard acceleration coming out of right hand turns. If I let off the gas or feathered the gas pedal it would smooth out. Not sure its a matter of right hand turns because at this track the left hand turns were much lower speed and I didn�t experience the hesitation. This condition has happened only briefly at previous tracks so I really didn�t pay much attention to it until this most recent occurrence which was pretty annoying. The track temperature at this event was about 100 degrees. Driving the car around town doesn�t have the hesitation. There are no DTC�s.
My question is in reference to your above statement regarding �pending codes�. Could you give me some hints as what to look for when I hook up my Durametric? Thanks in advance for your valued experience.
Jack
Hi Jack, ..Sounds like you are loosing fuel pressure or have water in the fuel...
With it being an intermittent problem and only happening at such a specific circumstance, it will be very difficult to verify and systematically troubleshoot...( ie. 4k-5k rpm, high-g, race track)
But you could do a sophisticated test rig/set-up. Install a manual pressure gauge with a very long line ( or use a high quality electric pressure gauge) ran out under the engine lid and over the top of the car (taped down) and onto the windshield.. Mount your phone/camera at the gauge then go recreate the symptoms to verify any pressure lose.
But first thing I would do on a 99C2 is to carefully remove the fuel filter without spilling/loosing any of the fuel contents, pour/empty into a clean glass jar to see if any rust/dirt, water, mud ect. was in the fuel filter..
Then of course install a new fuel filter and re-test....
As far as the Pending Codes, they are the same as other DTC's and show up under the same test, they just won't illuminate the CEL warning until they have been confirmed by happening two times and on two seperate dive cycles within 20 drive cycles of each other....
DTC's will either say "Present" or "Pending"in the subtitles........Ones that say Present either don't need confirming ( they are a level 1 Code) or they have already been confirmed ( level 2 code), Ones the say Pending are level 2 codes that have NOT been confirmed..
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