Misfires and rpm shudder (plugs, coils and battery replaced)
04-25-2022, 03:47 AM
#1
4th Gear
Thread Starter
Join Date: Apr 2022
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
Misfires and rpm shudder (plugs, coils and battery replaced)
Hi!
I'm new to this forum and new as a Cayenne owner. I Bought my Cayenne Turbo early this year and drove it a few hundred miles with no sign of trouble. Then I started noticing occasional small shudders on the rpm needle and slight "hesitations"(/misfires?) while driving. These grew worse over the next 500miles and I decided to replace all the ignition coil packs in February (the spark plugs were replaced Nov -21). Took the car out of the garage with a good feeling but only got about a mile before I had to confirm that the shudder and hesitation was still there.
Next step for me was to replace the battery, which turned out to be the original one (2012), for a new one of the same spec. Again, took it out of the garage with a good feeling -
and the car ran like a dream; alot more responsive on the throttle, alot less rpm shudder and no stumbles/misfires. For 25 miles.
Then slowly but surely all the previous problems came back over the next 300 miles (of which 200miles was a roadtrip on highways with steady speeds), and that's where I am at now.
This morning when I turned the ignition on the voltmeter read 11.9V, and when I drive off in comfort it goes up to 13.4-13.5. When i switch to sport mode it quickly climbs to 14.6-14.7. Also, the shudders and stumbles are somewhat less pronounced when in sport mode compared to comfort, but definitely still there and a problem.
So to sum it up:
Spark plugs, ignition coils and battery replaced. Ran perfectly (or close to) when i had just replaced the battery, but then gradually it got back to it's "old ways" of shuddering and stumbles/misfires. Runs a little better when in sport mode compared to comfort mode.
Does this sound like an alternator, and if so, is there an easy way to be certain of it? Or any other ideas on what could be causing this (since I'm not sure there is a direct connection between a bad/(semi-bad?) alternator and the misfires?)?
I'm new to this forum and new as a Cayenne owner. I Bought my Cayenne Turbo early this year and drove it a few hundred miles with no sign of trouble. Then I started noticing occasional small shudders on the rpm needle and slight "hesitations"(/misfires?) while driving. These grew worse over the next 500miles and I decided to replace all the ignition coil packs in February (the spark plugs were replaced Nov -21). Took the car out of the garage with a good feeling but only got about a mile before I had to confirm that the shudder and hesitation was still there.
Next step for me was to replace the battery, which turned out to be the original one (2012), for a new one of the same spec. Again, took it out of the garage with a good feeling -
and the car ran like a dream; alot more responsive on the throttle, alot less rpm shudder and no stumbles/misfires. For 25 miles.
Then slowly but surely all the previous problems came back over the next 300 miles (of which 200miles was a roadtrip on highways with steady speeds), and that's where I am at now.
This morning when I turned the ignition on the voltmeter read 11.9V, and when I drive off in comfort it goes up to 13.4-13.5. When i switch to sport mode it quickly climbs to 14.6-14.7. Also, the shudders and stumbles are somewhat less pronounced when in sport mode compared to comfort, but definitely still there and a problem.
So to sum it up:
Spark plugs, ignition coils and battery replaced. Ran perfectly (or close to) when i had just replaced the battery, but then gradually it got back to it's "old ways" of shuddering and stumbles/misfires. Runs a little better when in sport mode compared to comfort mode.
Does this sound like an alternator, and if so, is there an easy way to be certain of it? Or any other ideas on what could be causing this (since I'm not sure there is a direct connection between a bad/(semi-bad?) alternator and the misfires?)?
04-25-2022, 10:59 AM
#2
sounds more to me like either throttle body is dirty or MAF sensor is dirty, possibly vacuum leaks.
I had some weird symptoms like that , indicator lights it said were out, they were just fine, and key wouldn't come out. took battery to NAPA, they tested it and said it was fine, I replaced it anyways... everything works perfectly now...
you should be able to confirm voltage with voltmeter under the hood, and alternators can be tested as well.
I had some weird symptoms like that , indicator lights it said were out, they were just fine, and key wouldn't come out. took battery to NAPA, they tested it and said it was fine, I replaced it anyways... everything works perfectly now...
you should be able to confirm voltage with voltmeter under the hood, and alternators can be tested as well.
04-26-2022, 08:51 AM
#3
4th Gear
Thread Starter
Join Date: Apr 2022
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
sounds more to me like either throttle body is dirty or MAF sensor is dirty, possibly vacuum leaks.
I had some weird symptoms like that , indicator lights it said were out, they were just fine, and key wouldn't come out. took battery to NAPA, they tested it and said it was fine, I replaced it anyways... everything works perfectly now...
you should be able to confirm voltage with voltmeter under the hood, and alternators can be tested as well.
I had some weird symptoms like that , indicator lights it said were out, they were just fine, and key wouldn't come out. took battery to NAPA, they tested it and said it was fine, I replaced it anyways... everything works perfectly now...
you should be able to confirm voltage with voltmeter under the hood, and alternators can be tested as well.
But since the throttle body cleaning seems to be a simple procedure in comparison to replacing the alternator that's where I'll start!
Also, the Cayenne turbo doesn't have a MAF but an air sensor right? Is it possible to clean the sensor in the same way as the MAF (MAF cleaner, no touching) or is this generally not needed for the sensor as opposed to the MAF?
04-26-2022, 09:35 AM
#5
Mine does the same and I'm leaning towards the transfer case. Less pronounced in sport mode, but once warm it is noticeable there too. It def feels akin to a misfire as the car bucks, but I believe it's driveline related, i.e. transfer case.
04-26-2022, 11:09 AM
#6
Instructor
I also think you should consider the transfer case and have it diagnosed by a Porsche dealer who would replace it under extended warranty if that is indeed the case (no pun intended). Shuddering is the telltale sign of bad transfer case. Another sign of it is that it gets worse as the car warms up (really as the transfer case fluid gets hotter).
Trending Topics
04-26-2022, 12:27 PM
#8
From what I recall from other posts on the forum, it is normal to get a voltage increase in sport mode. The fact that the voltage is increasing in comfort and again in sport mode makes me think the alternator is working and responding to the ecu fine. Also, it always seems like battery/charge issues almost always throw a whole host of other flags/warning lights/bizarre behavior in the cayenne's, which I think usually occur before or alongside performance issues (further suggesting its not alternator or battery)
The fact the issue resolved with a battery change for a short while and also improves in sport mode makes me think its some bad/dirty sensors (maybe related to the throttle). If you have dirty sensors, resetting the ECU when you changed the battery may cause it to reestablish baseline settings that could compensate for dirty/bad sensors (maybe?). As well, I would imagine the sport mode opens various valves/flow paths further for enhanced performance, which may help compensate for the sensors give poor feedback at comfort settings. Thats my 2 cents; I could be way of base as my technical knowledge of these cars is pretty limited.
Also, as suggested, investigate more about the TC, especially if the 2012 are still under the extended warranty.
The fact the issue resolved with a battery change for a short while and also improves in sport mode makes me think its some bad/dirty sensors (maybe related to the throttle). If you have dirty sensors, resetting the ECU when you changed the battery may cause it to reestablish baseline settings that could compensate for dirty/bad sensors (maybe?). As well, I would imagine the sport mode opens various valves/flow paths further for enhanced performance, which may help compensate for the sensors give poor feedback at comfort settings. Thats my 2 cents; I could be way of base as my technical knowledge of these cars is pretty limited.
Also, as suggested, investigate more about the TC, especially if the 2012 are still under the extended warranty.
04-27-2022, 04:09 PM
#9
Thanks for your reply! I would lean towards your solution if only it wasn't for the clear improvement i felt after replacing the old battery with a new one, only to feel the car gradually go back to the previous problems pointed out. But to make sure I wasn't fooling myself I tried to charge the battery with my CTEK(5A)-charger last night. Looked at it after 2 hours and at that point it still wasn't fully charged, but this morning it was at least. As it was when I had just replaced the old battery with this new one, I once again could feel a clear improvement even though there still is some rpm shudder.
04-27-2022, 04:14 PM
#10
Mine just got a transfer case for similar symptoms for what it's worth.
05-28-2022, 03:35 PM
#11
4th Gear
Thread Starter
Join Date: Apr 2022
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
Thanks for your replies! The sheer amount of possible causes and the fact that I have an insurance covering "engine damage and related electronics" made me turn the problem over to my closest Porsche center.
One of the mechanics there drove the car and could see the RPM fluttering, though he said he could not feel the hesitations I described.
This, and the fact that the RPMs were steady according to their data collected at the same time as they saw the fluttering on the RPM gauge, led them to believe that the fault was with the gauges themselves (which I have seen isn't unheard of on the 958's).
After disassembling the throttle body and finding it was without fault, the service center replaced the entire instrument assembly.
The fact that I had felt hesitations/stumbles of course had me doubting that the instruments was at fault, but I convinced myself that I maybe had fooled myself into feeling that while looking at the RPMs fluttering.
Turns out this wasn't the case; when I got the car back I could tell there was no difference to the RPM fluttering, and now I'm even more sure that these have corresponding hesitations in the engine.
Also, I can add that the fluttering occurs at idle too, which tells me that the transfer case could be ruled out as the cause.
After visually inspecting for broken or disconnected hoses at the back of the intake manifold without luck I guess I'll have to return to my Porsche center and be at the mercy of the mechanic's ability to troubleshoot the problem accurately since there seems to be so many possible causes.
One of the mechanics there drove the car and could see the RPM fluttering, though he said he could not feel the hesitations I described.
This, and the fact that the RPMs were steady according to their data collected at the same time as they saw the fluttering on the RPM gauge, led them to believe that the fault was with the gauges themselves (which I have seen isn't unheard of on the 958's).
After disassembling the throttle body and finding it was without fault, the service center replaced the entire instrument assembly.
The fact that I had felt hesitations/stumbles of course had me doubting that the instruments was at fault, but I convinced myself that I maybe had fooled myself into feeling that while looking at the RPMs fluttering.
Turns out this wasn't the case; when I got the car back I could tell there was no difference to the RPM fluttering, and now I'm even more sure that these have corresponding hesitations in the engine.
Also, I can add that the fluttering occurs at idle too, which tells me that the transfer case could be ruled out as the cause.
After visually inspecting for broken or disconnected hoses at the back of the intake manifold without luck I guess I'll have to return to my Porsche center and be at the mercy of the mechanic's ability to troubleshoot the problem accurately since there seems to be so many possible causes.
05-28-2022, 06:59 PM
#12
Thanks for your replies! The sheer amount of possible causes and the fact that I have an insurance covering "engine damage and related electronics" made me turn the problem over to my closest Porsche center.
One of the mechanics there drove the car and could see the RPM fluttering, though he said he could not feel the hesitations I described.
This, and the fact that the RPMs were steady according to their data collected at the same time as they saw the fluttering on the RPM gauge, led them to believe that the fault was with the gauges themselves (which I have seen isn't unheard of on the 958's).
After disassembling the throttle body and finding it was without fault, the service center replaced the entire instrument assembly.
The fact that I had felt hesitations/stumbles of course had me doubting that the instruments was at fault, but I convinced myself that I maybe had fooled myself into feeling that while looking at the RPMs fluttering.
Turns out this wasn't the case; when I got the car back I could tell there was no difference to the RPM fluttering, and now I'm even more sure that these have corresponding hesitations in the engine.
Also, I can add that the fluttering occurs at idle too, which tells me that the transfer case could be ruled out as the cause.
After visually inspecting for broken or disconnected hoses at the back of the intake manifold without luck I guess I'll have to return to my Porsche center and be at the mercy of the mechanic's ability to troubleshoot the problem accurately since there seems to be so many possible causes.
One of the mechanics there drove the car and could see the RPM fluttering, though he said he could not feel the hesitations I described.
This, and the fact that the RPMs were steady according to their data collected at the same time as they saw the fluttering on the RPM gauge, led them to believe that the fault was with the gauges themselves (which I have seen isn't unheard of on the 958's).
After disassembling the throttle body and finding it was without fault, the service center replaced the entire instrument assembly.
The fact that I had felt hesitations/stumbles of course had me doubting that the instruments was at fault, but I convinced myself that I maybe had fooled myself into feeling that while looking at the RPMs fluttering.
Turns out this wasn't the case; when I got the car back I could tell there was no difference to the RPM fluttering, and now I'm even more sure that these have corresponding hesitations in the engine.
Also, I can add that the fluttering occurs at idle too, which tells me that the transfer case could be ruled out as the cause.
After visually inspecting for broken or disconnected hoses at the back of the intake manifold without luck I guess I'll have to return to my Porsche center and be at the mercy of the mechanic's ability to troubleshoot the problem accurately since there seems to be so many possible causes.
Going on a limb, have you considered excessive moisture in the gas? Ever tried some Chevron Techron Fuel Cleaner or Sea Foam Fuel Additive?
Personally, I tank up at 1/4 full. And I am very weary about where I get my gas. If possible, I get gas at Costco/Sam's. I never refuel when it is raining outside, or if I see fuel deliveries at the gas station. That's just me.
Replacing the entire instrument assembly to cure a RPM shudder sounds bizarre.
Last edited by Dr. G7; 05-28-2022 at 07:01 PM.
05-29-2022, 05:53 PM
#14
Instructor
What you wrote about voltages along with your other descriptions leads me to suspect the alternator. When electronics are doing strange things, the first thing you do is check the power supply. In a car, the power supply is your alternator.
06-15-2023, 03:30 PM
#15
4th Gear
Thread Starter
Join Date: Apr 2022
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
A long time later, but I'm still having troubles with my Cayenne..It's been in and out of the Porsche workshop many times but in the end the result is the same. I'll summarize here what hasn't worked and what I currently suspect to be the cause.
The workshop has ruled out the transfer case both by disconnecting the stepper motor and by trying to provoke it to slip during driving (braking and accelerating at a slow speed simultaneously, which they said causes it to slip if in a bad state).
All fuel injectors have been replaced.
Software (ECU?) has been updated.
Cylinders have been camera inspected and showed nothing the workshop deemed out of the ordinary.
Valves have been inspected and did have "some" carbon buildup (?) on them, but the workshop deemed them unlikely to be the cause.
Now, to the light at the end of the tunnel (I hope): The day after the injectors were replaced and the software updated I got a check engine light within 2min after first start-up. I was driving slow and cautiously and the light went on without any other indication to me that anything had just happened. About 30sec later the light went out again. I took the car to the same Porsche workshop and they said they could see a fault code related to a knock sensor, but that it was now historic and that it was unrelated to the problems/symptoms displayed by my car.
I took the car home without action but it got me thinking about, and reading up on, knock sensors. The way I understand it, a knock sensor could potentially malfunction in such a way that it is "over-sensitive", which would make the ECU think there were engine knocks when there in fact aren't, right?
And if so, I also understand that ECU's of some manufacturers learn the circumstances (load, RPM etc) surrounding these supposed knock events and try to avoid them happening again in the future by (indirectly, by ignition timing and maybe other adjustments) limiting performance, correct?
This would explain why the car feels a lot better after resetting the "ECU learning" (either directly by the workshop or by disconnecting the battery to replace it with a new one) and gradually gets worse, as well as the lack of power I feel my Cayenne has. I don't know if it can explain the shudders though, or if this maybe is the direct result of the ECU momentarily adjusting engine parameters to avoid "learned knock events".
Please poke holes in my suspicion of it being an "over-sensitive" knock sensor if you see any problems with the theory, as my understanding of the knock sensor and its interplay with the ECU may be incorrect and incomplete.
The workshop has ruled out the transfer case both by disconnecting the stepper motor and by trying to provoke it to slip during driving (braking and accelerating at a slow speed simultaneously, which they said causes it to slip if in a bad state).
All fuel injectors have been replaced.
Software (ECU?) has been updated.
Cylinders have been camera inspected and showed nothing the workshop deemed out of the ordinary.
Valves have been inspected and did have "some" carbon buildup (?) on them, but the workshop deemed them unlikely to be the cause.
Now, to the light at the end of the tunnel (I hope): The day after the injectors were replaced and the software updated I got a check engine light within 2min after first start-up. I was driving slow and cautiously and the light went on without any other indication to me that anything had just happened. About 30sec later the light went out again. I took the car to the same Porsche workshop and they said they could see a fault code related to a knock sensor, but that it was now historic and that it was unrelated to the problems/symptoms displayed by my car.
I took the car home without action but it got me thinking about, and reading up on, knock sensors. The way I understand it, a knock sensor could potentially malfunction in such a way that it is "over-sensitive", which would make the ECU think there were engine knocks when there in fact aren't, right?
And if so, I also understand that ECU's of some manufacturers learn the circumstances (load, RPM etc) surrounding these supposed knock events and try to avoid them happening again in the future by (indirectly, by ignition timing and maybe other adjustments) limiting performance, correct?
This would explain why the car feels a lot better after resetting the "ECU learning" (either directly by the workshop or by disconnecting the battery to replace it with a new one) and gradually gets worse, as well as the lack of power I feel my Cayenne has. I don't know if it can explain the shudders though, or if this maybe is the direct result of the ECU momentarily adjusting engine parameters to avoid "learned knock events".
Please poke holes in my suspicion of it being an "over-sensitive" knock sensor if you see any problems with the theory, as my understanding of the knock sensor and its interplay with the ECU may be incorrect and incomplete.