22 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCH996 idles low and sometimes stalls!
Leading reported evidence
Replace by the dealer a week ago
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
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Performed · outcome unconfirmed
I just have the battery changed by the dealer a week ago.
Leading evidence: 'Replace by the dealer a week ago' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check battery' (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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Suggestion
Check the vaccum boost connection for the brake booster.
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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Suggestion
Great stuff, that will clean the injectors thoroughly.
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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0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
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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.
22 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.
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Generation: 20261026T052503Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
I have a 2002 996 coupe and occasionaly while braking the car will stall while i am coming to the light, most of the time i have the clutch pedal down. Also, when I brake hard the rpms fluctuate downward. Does anyone know what my cause this? Or if the fluctuation of the rpms in unusual? Please respond.
There have been reports of a similar problem from other owners. Check out this topic on CFG's 996 Discussion Board at
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I test drove a 2002 996 C2 coupe (18" wheels) yesterday, and asked the dealer about the reported problem. They already knew about it, and said it was an idle logic problem in the Motronic.
I am encountering a similar problem. My car is a tip. When I brake hard, the rpms fluctuate downward and the car will stumble or stall (this will not happened once the car is warmed up). If it is an idle logic problem in the Motronic, then can it be cured (e.g. re-promgramming the computer)? Apart from this possibility, could it be also due to some vacuum leak? Thanks in advance for your help.
There are a couple of factors. MAF could very well be the culprit, also the spark plugs (depending on miles)...bad gas could also be the culprit.
For good measure, run a bottle of Techron (available at a local auto store) through in combination with the next full tank. Great stuff, that will clean the injectors thoroughly.
That would be the first step. if you still have the problem, stop a local dealership/Independant Porsche shop for a check. If it's the MAF it may simply need to be replaced.
Chad
THERE IS A CONNECTION IN THE BRAKE BOOSTER VACUUM LINE THAT IS BEHIND THE HEADLIGHT GOING THROUGH THE FRONT TRUNK BULKHEAD.IT HAS BEEN A SOURCE OF LEAKS IN THE PAST(YOU NEED TO CHECK BOTH SIDES).ALSO IF I REMEMBER CORRECTLY THERE WAS A BULLETIN(MAYBE A RECALL)ON SOME 02'S FOR THIS PROBLEM.
Thanks for your views guys.
What actually happened is that when braking to a stop (during the first 5 mins after morning start-up), the idle will drop to where the car is about to stall, then bounce up and around until it finds the idle. Do you think a leak in the brake booster vacuum line can cause the rpm to run low and thus stalling the engine? When the car is warmed up, the stalling problem will go away. Do you think it is possible that the seals or rubber hosing expand from the heat and therefore reducing the leak? Will a vacuum leak in the brake booster screw up the way the engine runs?
Dear 1999Porsche911,
The problem is that I don't seem to have any braking problem. The brakes are working fine. Anyway, I want to provide you with a little update on the stalling problem. Acutally if I don't turn on the A/C, headlights and radio (with the battery level slightly below 14), then the rpm will only drops a little (still above 500) and stalling will not happen even when braking. Only when I have all the electrical items turned on (especially the A/C - with the battery level drops to slightly above 12), then the problem will appear. I am wondering whether the stalling has anything to do with the possible faulty A/C fan (which draws a lot of electricity from the battery). Yesterday, I discover that there is ticking noise coming from the back of the instrument panel area. When I have the A/C turned on, the ticking noise appears after the car is warmed up. Once I turn off the A/C, the ticking noise will disappear. I've tried a couple times (ie turn on and off the A/C) and the same has happened so I guess the ticking noise should be from a faulty A/C fan behind the instrument panel. Furthermore, sometimes there will be a loud "squeaking" noise from behind the instrument panel when I turned on the A/C. Any views?
Do you know where exactly is the alternator? There is always a loud plastic rubbing noise from around the centre of the engine when I start the car. It will last for about 5-10 seconds. Do you think this may be the sound of a faulty alternator or bad alternator belt?
Hi guys,
I've heard that one can actually try testing the brake pedal to see if there is a leak. Isn't it that when you step on the brake pedal a couple of times after the engine is off, the brake pedal will become hard due to the release of vacuum in the booster. I've tried that but my brake pedal did not get harden and I can continuously press onto the brake pedal as if the engine is running. Does it mean that there is a vacuum leak in the brake booster?
As to the alternator, it seems that it is still working alright (although the plastic rubbing noise continues for the first 5-10 seconds after start-up). Everytime when I start the engine, the battery level will be around 12V before ignition is on and 14V after ignition is on (of course, with A/C, lights and radio off). Once I turn on the lights, A/C and radio, then the battery level will drop to around 12-12.5V. I am not sure if this is normal.
The frustrating thing is that the dropping of the rpm while braking only happens during the first 5-10 mins drive after start-up. Once the engine is warmed-up, this problem will disappear (at least it won't be as bad which causes the engine to shudder or stall).
Yesterday, I placed my foot on the brake pedal when starting the engine but the brake pedal did not depress or drop. Does it mean that the brake booster is not functioning properly?
