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If you do decide to disconnect the battery, you could touch the two lead cables together to drain any residual capacitance in the vehicles electronics, or wait 5-10 mins with the battery disconnected.
It’s best practice to disconnect the negative cable first when handling the battery.
On electronics, I’ll sometimes try to turn them on while unplugged to try to drain any charges.
Last edited by Mike Murphy; 07-12-2024 at 10:11 AM.
If you do decide to disconnect the battery, you could touch the two lead cables together to drain any residual capacitance in the vehicles electronics, or wait 5-10 mins with the battery disconnected. I would disconnect the positive cable and touch it to the negative side cable. Not vice versa - be careful not to confuse the two.
I can't see how the result achieved by 'touching positive to negative' is any different from that by the 'vice versa'.
Is it to do with the battery being a large 'sink' and thus less or no spark when touching?
I can't see how the result achieved by 'touching positive to negative' is any different from that by the 'vice versa'.
Is it to do with the battery being a large 'sink' and thus less or no spark when touching?
No difference. I edited my post because I must have had dyslexia that day and was backwards.
The reason to disconnect the negative cable first is because a ground short could occur if the positive side touches the body (which is grounded) with a metal wrench.
My guess is with it being 100+ degrees air temp, the MAFS is sensing the temperature and not allowing the car to rev. as it doesn't need to build temp. I live in Houston and my 991.1 does the same thing....but when the air temp was lower (60's) the car would rev high on start up and level after about 30 seconds.....I wouldn't worry about it.
I'm in Phoenix as well - I recently bought a fairly low mileage 996 C2, just had it fully serviced (new plugs, 997 coils, oil change, etc, etc) and mine does the exact same thing when starting it for the first time each day. The temperature in my garage is 108 currently. I'm inclined to agree with Viper after reading through this thread - my car runs perfectly in every other way so I have no issue waiting for temperatures to drop to see if my car decides it's actually now cool enough to bother keeping the rpms up when first starting.
I'm in Phoenix as well - I recently bought a fairly low mileage 996 C2, just had it fully serviced (new plugs, 997 coils, oil change, etc, etc) and mine does the exact same thing when starting it for the first time each day. The temperature in my garage is 108 currently. I'm inclined to agree with Viper after reading through this thread - my car runs perfectly in every other way so I have no issue waiting for temperatures to drop to see if my car decides it's actually now cool enough to bother keeping the rpms up when first starting.
Interesting! Sounds like that’s the reason.
Little tidbit of info: the Porsche M96 996 engines start with an initial higher rev blip is largely due to the oil pump system design. That blip is meant to ensure the pump can lift all oil quickly on startup to critical components. At 100F+, the oil is probably thin enough that this is not required.
If it bothers you, you could blip the throttle yourself. I actually hold my revs at 1500-2000 RPM on cold start myself, for 5-10 seconds. because otherwise, I get a lot of rattling at idle when the engine is cold. I’d rather have more oil circulating faster in any cold start situation. Similar to: ‘start the car and drive off immediately,’ which is good practice for these engine anyway.
I’m just now seeing this thread…I made a thread about a similar issue my car is having…I did a search and older threads showed up, but not this one…then I just scroll down and here’s the thread…wtf
An update - I did a cold start yesterday at 6:00am and it started normally - higher revs, typical start that I'd expect from a warm start as well. I immediately checked the ambient temperature and my garage was at 95 degrees.
Thirteen hours later - 7:00pm - I did another (relatively) cold start and the engine did not do the higher revs; it held the lower idle as described by the op and myself in earlier posts. Again I checked the ambient temperature - my garage was at 105 degrees.
I continue to agree with Viper's post. Looks like a temperature thing.
I wonder how the Porsche Engineers decided what temperature would indicate the engine was already warmed up - looks to be somewhere between 38-40C* - I envision them saying, "there's no way any sane person would be anywhere where the LOW temperature is 40C! Let's use that!"
*Celsius used in my imaginings because Europe. Yes, they're all wearing white lab coats too.
There’s are still plenty of places in Europe that don’t have AC - richer regions too. It’s been unseasonably hot there already this summer and last year was worse.
105F is presumably a car that was started just recently and driven a short distance, so they assumed oil lubrication is pretty much already present, which it’s not. So that’s why I would manually hold 1200-1800 RPM on your 105F cold start car for a few seconds after start.
In the end, probably doesn’t even matter, but we Porsche types are a bit ****.
Subscribing because my '99 just did this to me yesterday after sitting in the airport parking lot for 48 hours. Ambient temp was only in the high 70's, with high humidity though. Very odd.
Jumping back into this thread, and not surprisingly, @Porschetech3 seems to be correct. The car went back to the PO's shop for a bit to fix one lingering issue, so I only just got it back. While it was up there (N. Arizona) I had them check on this issue, and naturally they couldn't reproduce it, since it's in the mid-80s up there with overnight lows in the 60s. Works totally fine in that weather.
Next question for the group here is which component actually contains the check valve? Is it the fuel pump itself or the upper sender/regulator piece? I already bought the new pump since I found it really cheap at my dealer, but now that I have it apart, I'm starting to question if that's the right part to replace. Another side note - what's the best way to take care of debris in the fuel tank? Seems to be a lot sitting down there.
To hold fuel pressure on the injector rails it needs 2 check valves.....one at the outlet of the fuel pump and one on the outlet of the pressure regulator ..
On the 996.1 cars the pressure regulator is on the fuel rail on the engine, on the returnless 996.2 cars the pressure regulator is in the fuel tank made into the fuel sending unit/housing...
Got it. Makes me feel a little better that there's one in both pieces inside the tank (996.2 over here). I only fully realized the scope of my misunderstanding once I pulled it out this morning. Basically shooting in the dark here on which it is, I guess. We'll know in the AM if it was the pump itself. Very much hoping it's not an injector leaking down. That seems detrimental to other parts of the engine.
07-11-2024, 08:03 PM
