Engine stumble/hesitation around 2500 RPM?
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I'm not trying to diminish your intent with the well-meaning contributions to the problem, but I think you nailed it on the head right there in my quote above. You have convinced yourself that you found the issue. Unfortunately, you haven't convinced anyone else. You can repeat yourself ad nauseum, but that's not going to change most minds.
It seems that the bad gas caused your car to set a fault. Good gas removed the fault. To my knowledge, no one experiencing this surging issue has gotten any kind of fault code or check engine light.
It seems that the bad gas caused your car to set a fault. Good gas removed the fault. To my knowledge, no one experiencing this surging issue has gotten any kind of fault code or check engine light.
And to be clear I couldn't give a damn as my intention isn't to convince YOU of anything. Then again this thread is 400 posts long and hasn't said anything new or interesting in about a year. So it is back to the much more interesting exhaust and wheel posts.
But hey, sorry for irritating you.
You have a great day
Last edited by scatkins; Apr 23, 2015 at 04:10 PM.
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If I was using just one brand of fuel I might agree with you.
Also, to Runner's point, above 3500 RPM my car is AMAZING. Perfectly smooth.
And one more point: Yes, using a different octane might bring to the surface timing issues and *replicate* the problem. I think we're all saying it's a timing/fuel issue. But there are so many factors that the computer uses to determine timing and fuel delivery. It could be a temperature sensor. It could be an oxygen sensor. But because I have tried many brands of gasoline I have determined to my satisfaction that fuel alone is not the problem, and merely changing the type of fuel used will therefore not solve this problem.
In fact, when this stumbling first started, my immediate gut reaction was "bad gas". I've run older cars on bad gas and gas that got water in it... it felt just like that.
Also, to Runner's point, above 3500 RPM my car is AMAZING. Perfectly smooth.
And one more point: Yes, using a different octane might bring to the surface timing issues and *replicate* the problem. I think we're all saying it's a timing/fuel issue. But there are so many factors that the computer uses to determine timing and fuel delivery. It could be a temperature sensor. It could be an oxygen sensor. But because I have tried many brands of gasoline I have determined to my satisfaction that fuel alone is not the problem, and merely changing the type of fuel used will therefore not solve this problem.
In fact, when this stumbling first started, my immediate gut reaction was "bad gas". I've run older cars on bad gas and gas that got water in it... it felt just like that.
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In SC, we can purchase high-octane non-ethanol gasoline by choice. It does not solve the "fishing line tug" problem. Doesn't matter what brand. Techron or other additives have no effect. I've only had ethanol-tainted gasoline in the car about 6 times in 2.5 years. That didn't help either.
Driving hard or soft does not eliminate the issue. The issue is always present as you "ease" through the 2-3K RPM range during regular street driving. It's not there through rapid acceleration. Gets frustrating quite often.
Check out pure-gas.org or the "ethanol free" app for IOS to see SC's availability. It's readily available all over the state. Wish Porsche would tell us what's wrong.
Driving hard or soft does not eliminate the issue. The issue is always present as you "ease" through the 2-3K RPM range during regular street driving. It's not there through rapid acceleration. Gets frustrating quite often.
Check out pure-gas.org or the "ethanol free" app for IOS to see SC's availability. It's readily available all over the state. Wish Porsche would tell us what's wrong.
Last edited by Curvfun; Apr 27, 2015 at 07:08 AM.
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Pump 93 is 93.0. There is no tolerance for the spec when it leaves the refinery. Octane doesn't degrade with tine or handing, so expect no variability based on where or what brand of gas you use. The ONLY possible issue with gas is water in it, this is rare and if you have this issue, you will know it right away.
2500 rpm and light load is the LEAST demanding engine operating region, creates no demand for octane and is not going to cause knock or ignition timing retardation. Even 91 octane will not cause an issue. 91 might cause reduced performance under high load, but you would need a stop watch to notice.
I feel sympathy for those that have this issue and their frustration with Porsches denial. My fingers stay crossed as my car doesn't do it.
2500 rpm and light load is the LEAST demanding engine operating region, creates no demand for octane and is not going to cause knock or ignition timing retardation. Even 91 octane will not cause an issue. 91 might cause reduced performance under high load, but you would need a stop watch to notice.
I feel sympathy for those that have this issue and their frustration with Porsches denial. My fingers stay crossed as my car doesn't do it.
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Sorry for the late reply. Have been busy and has had problem with the iPad loading 6 sp lately.
Anyways, I think the acceleration starts around 2000 rpm. I tried to replicate it today and it didn't do it. So, no idea what's going on. Sometimes, it almost felt like it is a traction issue without PTM kicking in.
I can't say my car consistently stumbles. But there are times that it definitely does and I can feel something is up.
Car is two years old now with close to 17,000 miles. If this does not get worse, I can live with it. With the car being the last gen of NA flat 6, I am hoping I might keep it longer. If the stumble issue rears its ugly head and become bothersome outside of warranty (not that PAG is admitting a problem), than I might have to jump onto the turbo bandwagon.
Anyways, I think the acceleration starts around 2000 rpm. I tried to replicate it today and it didn't do it. So, no idea what's going on. Sometimes, it almost felt like it is a traction issue without PTM kicking in.
I can't say my car consistently stumbles. But there are times that it definitely does and I can feel something is up.
Car is two years old now with close to 17,000 miles. If this does not get worse, I can live with it. With the car being the last gen of NA flat 6, I am hoping I might keep it longer. If the stumble issue rears its ugly head and become bothersome outside of warranty (not that PAG is admitting a problem), than I might have to jump onto the turbo bandwagon.
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For me it's obvious in three modes:
1) Trying to maintain constant velocity at an RPM near 2300. There is a sensation that many of us describe as a "fish tugging on your line" if you're a fisherman you'll get it.
2) When I accelerate with medium throttle through the 2K RPM range I get stumbles until I hit 3K RPM.
3) When I do hit 3K RPM there is often a much larger stumble.
Once past 3200 RPM for me everything is just perfect.
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Has anyone tried OBDII technology for help on this issue?
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Unfortunately it's too subtle to capture on video or audio. It's not apparent in the tach. You would need some diagnostic equipment set up most likely. It's a seat-of-the-pants feeling.
For me it's obvious in three modes:
1) Trying to maintain constant velocity at an RPM near 2300. There is a sensation that many of us describe as a "fish tugging on your line" if you're a fisherman you'll get it.
2) When I accelerate with medium throttle through the 2K RPM range I get stumbles until I hit 3K RPM.
3) When I do hit 3K RPM there is often a much larger stumble.
Once past 3200 RPM for me everything is just perfect.
For me it's obvious in three modes:
1) Trying to maintain constant velocity at an RPM near 2300. There is a sensation that many of us describe as a "fish tugging on your line" if you're a fisherman you'll get it.
2) When I accelerate with medium throttle through the 2K RPM range I get stumbles until I hit 3K RPM.
3) When I do hit 3K RPM there is often a much larger stumble.
Once past 3200 RPM for me everything is just perfect.
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There must be an audible engine noise that is discernible from being normal. I have been listening intently for anything out of the ordinary through this rpm band, and a feeling of fish tugging as you describe, I got nothing. If someone has a definitive video, it would go a long way as an argument for a collective issue for Porsche to address.
https://www.dropbox.com/s/qjjgy5y04m16khl/gp1.m4a?dl=0
https://www.dropbox.com/s/ydom49mvgu5r5ph/gp2.m4a?dl=0
I think you'll notice the very distinct pitch change transitioning aprox. 2500 rpm.
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Here are a couple of clips I recorded (External mic positioned near exhaust tips, PSE on):
https://www.dropbox.com/s/qjjgy5y04m16khl/gp1.m4a?dl=0
https://www.dropbox.com/s/ydom49mvgu5r5ph/gp2.m4a?dl=0
I think you'll notice the very distinct pitch change transitioning aprox. 2500 rpm.
https://www.dropbox.com/s/qjjgy5y04m16khl/gp1.m4a?dl=0
https://www.dropbox.com/s/ydom49mvgu5r5ph/gp2.m4a?dl=0
I think you'll notice the very distinct pitch change transitioning aprox. 2500 rpm.
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Yes, the first audio, one can hear what seems like a fuel starvation noise. Sounds almost like the engine is not getting fuel. I definitely don't have this problem. Serious issue for everyone that does have it.
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I truly think PCNA could begin to understand the problem if they would allow a tech to manually actuate each VarioCam bank with their PIWIS tester, which should confirm proper operation. Or from a conspiracy standpoint, perhaps they've already done this and are aware of the issue, but realize the fix would be very costly.
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Just had my car in for annual service (has it really been two years? sheesh). Anyway, I once again reported my issues. I feel like I just need to keep the paper trail going in case something catastrophic happens after my warranty runs out.
My four problem areas have been these:
1) Rougher idle in non-sport mode. Hunts from 600-700. (Sport mode idle is still pegged at 800 exactly.)
2) Rough acceleration. In the entire 2000-3000 RPM range my acceleration (medium to heavy) has been rough. Think merging onto a highway or just pulling away from a light.
3) Hesitation at 2300 RPM under light throttle. Trying to maintain constant speed results in the "fish tugging at your line" feeling.
4) Larger stumble right at 3000 RPM. This is most likely a variocam issue.
Well, after only 24 hours, it seem like issues (2) and (3) have gone away or been reduced so they are not noticeable. Especially (2). That rough acceleration just made me feel like I had a little lawnmower engine in my car sometimes when trying to accelerate. It was awful. Also, as for (4), it seems like the transition has been smoothed out a bit so I no longer feel the "clunk" that I used to (it would sometimes lurch me forward in my seat).
They updated my DME. That's the only thing they did. So here's once again hoping it really is a software issue.
Here are the tech notes: "REPROGAMED DME TO LATEST SOFTWARE VERSION WITH TESTER VERSION 15.650 TEST DROVE VEHICLE WORKING PROPERLY AT THIS NO HESITATIONS FELT AND VEHCILE IDLES AS COMPAIRED TO LIKE VEHICLES".
Crossing my fingers. But yesterday and today it has felt like a totally new car. I am actually enjoying the drive now.
My four problem areas have been these:
1) Rougher idle in non-sport mode. Hunts from 600-700. (Sport mode idle is still pegged at 800 exactly.)
2) Rough acceleration. In the entire 2000-3000 RPM range my acceleration (medium to heavy) has been rough. Think merging onto a highway or just pulling away from a light.
3) Hesitation at 2300 RPM under light throttle. Trying to maintain constant speed results in the "fish tugging at your line" feeling.
4) Larger stumble right at 3000 RPM. This is most likely a variocam issue.
Well, after only 24 hours, it seem like issues (2) and (3) have gone away or been reduced so they are not noticeable. Especially (2). That rough acceleration just made me feel like I had a little lawnmower engine in my car sometimes when trying to accelerate. It was awful. Also, as for (4), it seems like the transition has been smoothed out a bit so I no longer feel the "clunk" that I used to (it would sometimes lurch me forward in my seat).
They updated my DME. That's the only thing they did. So here's once again hoping it really is a software issue.
Here are the tech notes: "REPROGAMED DME TO LATEST SOFTWARE VERSION WITH TESTER VERSION 15.650 TEST DROVE VEHICLE WORKING PROPERLY AT THIS NO HESITATIONS FELT AND VEHCILE IDLES AS COMPAIRED TO LIKE VEHICLES".
Crossing my fingers. But yesterday and today it has felt like a totally new car. I am actually enjoying the drive now.