When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I sort of had a similar issue you are describing. Mine would run for about 10min and shut down, the second time it would only run for a about 30seconds and stall. After an ecu reset it would run for about 10min and stall again. Turned out that one of my fuel pumps in the tank had died and also had corrosion on pump power connector. The Porsche shop I took the car to diagnosed it ended up draining the tank (we did fuel analysis) and replacing fuel pump assembly. We think that because I don't drive the car a lot, maybe 1000 miles a year, the ethanol in the fuel probably caused corrosion over time and burning out one of the pumps.
Brought car to 2 different Porsche specialists who are stumped after connecting it to PIWIS and starting it and actively watching the codes and logging the injector duty cycle and fuel trims. Problem still exists after disconnecting methanol pump and reloading stock tune. It's crazy that disconnecting the battery ground corrects the problem and it runs perfectly until I turn off car and restart it. And when I say it runs perfectly, I mean that it runs flawlessly without any roughness or power loss.I am so annoyed at this point.
1. After running the car for any length of time (short to medium to long trips), once the ignition is turned off, the car starts for 10 seconds then stalls
2. Car starts and runs perfectly after a disconnect and reconnect of the battery until the next stop.
3. At no time when it is running does the car ever not run perfectly.
4. You have looked at the obvious values as it was stalling and none of them fluctuated before the engine dies.
Are these symptoms able to be replicated consistently?
Does behavior change if you leave the key in the ignition switch and try to restart it?
Have you ever looked at faults just after disconnect/reconnecting and running the car vs. just after the stop vs. as you are trying to restart it?
Has anyone ever looked at the anti theft components of the car? I have zero knowledge of how antitheft and immobilizers work, but it seems you have some sort of electrical issue where de-powering the car power circuit allows things to run normally. So some circuit/sensor is not being completed when you stop the car after re-powering the circuit. However my gut tells me if it was something like this you would not even be able to crank the engine. Doing a bit of searching I see the antitheft mentioned, but not in combination with running/stalling, so I don't want to send you on a wild goose chase.
I also see corrosion mentioned, so the suggestion of checking every ground (and maybe other power connections) is less of a wild goose chase, but may be a daunting task if you start tearing the center console apart in addition to looking at the engine grounds/power connections. What I don't see (at least yet, I'm going to continue to search) is the car running then stalling after 10 seconds.
My only other thought is this: The car starts/stalls after 10 seconds. This means it is getting fuel/fire/air adequately to run for those 10 seconds, so maybe it is fuel.
Fuel - it runs fine for 10 seconds, so unless some electrical issue is on the bleeding edge of failing exactly the same timing and is in some way related to solving it by reconnecting the battery (in my opinion this would cover air since the MAF may be the only thing to kill an engine for air related issues - though my experiences with MAF's are ****ty running) I think the engine is burning the fuel in the lines then running out of fuel. You might be able to test this. Does the car ever restart successfully if you start it and quickly shut it off after the "fix"? If so, then maybe you can do this sequence twice, but on the second attempt, pull the fuel pump fuse(s) and start. If it runs for 10 seconds, this might help focus your troubleshooting. If it doesn't, then yank the fuses as it is running, does it stall after 10 seconds? Maybe this points in a direction.
This is only my opinion based on reading this thread, my own limited mechanical knowledge and doing some searching. I could be totally off base and I don't want to add to your frustration by sending you down a rabbit hole. The good thing is, there is a cause for this, so all hope is not lost. I forget who and exactly how it's phrased, but there is something about the journey to a solution being valuable. Of course they probably never tried to troubleshoot some odd ball mechanical issue.
I also just had an issue where my car would only run for 10 sec above 3/4 of a tank. Upon battery pull the car stops stalling, until the next restart.
Luckily, Todd from Promotive saved the day, and it turned out that one of my fuel pumps was failing! The connector also melts, so you want to replace the firewall flang connection as well. You need to replace #7 & 5 otherwise you will be going through fuel pumps like crazy.
Along with the associated connector on the end of the pump harness (5)
Underside of the top flange after a connector had melted (7)
Knowage and pictures courtosy of Todd from Protomotive!!
1. After running the car for any length of time (short to medium to long trips), once the ignition is turned off, the car starts for 10 seconds then stalls
2. Car starts and runs perfectly after a disconnect and reconnect of the battery until the next stop.
3. At no time when it is running does the car ever not run perfectly.
4. You have looked at the obvious values as it was stalling and none of them fluctuated before the engine dies.
Are these symptoms able to be replicated consistently?
Does behavior change if you leave the key in the ignition switch and try to restart it?
Have you ever looked at faults just after disconnect/reconnecting and running the car vs. just after the stop vs. as you are trying to restart it?
Has anyone ever looked at the anti theft components of the car? I have zero knowledge of how antitheft and immobilizers work, but it seems you have some sort of electrical issue where de-powering the car power circuit allows things to run normally. So some circuit/sensor is not being completed when you stop the car after re-powering the circuit. However my gut tells me if it was something like this you would not even be able to crank the engine. Doing a bit of searching I see the antitheft mentioned, but not in combination with running/stalling, so I don't want to send you on a wild goose chase.
I also see corrosion mentioned, so the suggestion of checking every ground (and maybe other power connections) is less of a wild goose chase, but may be a daunting task if you start tearing the center console apart in addition to looking at the engine grounds/power connections. What I don't see (at least yet, I'm going to continue to search) is the car running then stalling after 10 seconds.
My only other thought is this: The car starts/stalls after 10 seconds. This means it is getting fuel/fire/air adequately to run for those 10 seconds, so maybe it is fuel.
Fuel - it runs fine for 10 seconds, so unless some electrical issue is on the bleeding edge of failing exactly the same timing and is in some way related to solving it by reconnecting the battery (in my opinion this would cover air since the MAF may be the only thing to kill an engine for air related issues - though my experiences with MAF's are ****ty running) I think the engine is burning the fuel in the lines then running out of fuel. You might be able to test this. Does the car ever restart successfully if you start it and quickly shut it off after the "fix"? If so, then maybe you can do this sequence twice, but on the second attempt, pull the fuel pump fuse(s) and start. If it runs for 10 seconds, this might help focus your troubleshooting. If it doesn't, then yank the fuses as it is running, does it stall after 10 seconds? Maybe this points in a direction.
This is only my opinion based on reading this thread, my own limited mechanical knowledge and doing some searching. I could be totally off base and I don't want to add to your frustration by sending you down a rabbit hole. The good thing is, there is a cause for this, so all hope is not lost. I forget who and exactly how it's phrased, but there is something about the journey to a solution being valuable. Of course they probably never tried to troubleshoot some odd ball mechanical issue.
Ed
You are correct in your assessment of the symptoms. The only code that is unusual is the P1265 crash signal code that intermittently pops up but is not associated with the car stalling. I haven't tried recycling the ignition after restarting the car after the battery "fix". Gonna look at my fuel pump harness and connection. Checking all grounds seems like a daunting task.
Wow, I bet that's it. Does the car have more than 1 fuel pump?
Yes, the pump housing (5) has two pumps in it. They oscillate between primary and secondary based on fuel level and other factors.
When the car first starts, it uses both pumps for about 10 seconds. Then decides what pump to use; when the tank is above 3/4 the secondary becomes the primary. Doing a 5-minute battery pull seems to reset the computer so that the primary stays as the primary.. until restart.
They seem to fail around 75k miles. Not sure if the pump fails and melts the connection or the the connection fails and burns out the pump.
09-21-2023, 02:57 AM
