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If a 5-year-old battery could do that, I think it would be pretty obvious. You have a bad coil or a loose connection.
Continuing to drive a misfiring engine isn't good for it.
Agreed re battery and driving. Mostly doing process of elimination and battery about due anyway. Forgot to mention on this thread that I had previously gotten some codes for misfiring so switched 2 of the coils and plugs between cylinders. Those codes did not come back up and I wonder if it could be the ECU?
Agreed re battery and driving. Mostly doing process of elimination and battery about due anyway. Forgot to mention on this thread that I had previously gotten some codes for misfiring so switched 2 of the coils and plugs between cylinders. Those codes did not come back up and I wonder if it could be the ECU?
Since you are competent with automobiles, before taking it to a shop, I would agree with others to simply replace all the coils. .. if that doesn't work, then I would take it to a shop.
Since you are competent with automobiles, before taking it to a shop, I would agree with others to simply replace all the coils. .. if that doesn't work, then I would take it to a shop.
Thanks, thats what I'm thinking. Work done today, Posting more tomorrow.
If you had misfire Pcodes on all cylinders previously, I would think it’s unlikely that all coils failed at the same time.
What is the mileage of the car?
Does it also misfire at idle?
Does anyone know if the 991.2 Carrera engine has an air mass flow sensor after the air filter box? If you have an intake leakage after the air mass flow sensor but before the throttle body, at idle, the engine will suck more air than is read by the air mass flow sensor and you will have misfire at idle.
Check if the ECU pins are not bent or damaged.The terminal issue you mentioned could be a lead. Has anyone got a wiring diagram of a 991.2 Carrera engine ECU?
If you had misfire Pcodes on all cylinders previously, I would think it’s unlikely that all coils failed at the same time.
What is the mileage of the car?
Does it also misfire at idle?
Does anyone know if the 991.2 Carrera engine has an air mass flow sensor after the air filter box? If you have an intake leakage after the air mass flow sensor but before the throttle body, at idle, the engine will suck more air than is read by the air mass flow sensor and you will have misfire at idle.
Check if the ECU pins are not bent or damaged.The terminal issue you mentioned could be a lead. Has anyone got a wiring diagram of a 991.2 Carrera engine ECU?
No P codes, here is an excerpt of codes info from initial reading:faults is 007010 "check engine control unit fault memory content", 00A008 "PSM failure", 00A016 "check engine" but not all the codes I found begin with a letter and my iCarsoft OBD is not giving me options to explain them. It only wants to see a letter, followed by 4 letters or digits Yes, misfire at idle, I took the bumper off again and inspected the air lines related to the air filter replacement, everything looked good x one POSSIBLE connection. Will clear codes again and start, warm up etc. I guess could be an O2 sensor but am getting no codes related or I don't know what values are supposed to be in the data readings. Again, no P codes, only these codes now (after clearing the original codes): 00A016 (inst. cluster), and 000401 and "engine control fault" on the console. Thanks for everyone's help and input.
No P codes, here is an excerpt of codes info from initial reading:faults is 007010 "check engine control unit fault memory content", 00A008 "PSM failure", 00A016 "check engine" but not all the codes I found begin with a letter and my iCarsoft OBD is not giving me options to explain them. It only wants to see a letter, followed by 4 letters or digits Yes, misfire at idle, I took the bumper off again and inspected the air lines related to the air filter replacement, everything looked good x one POSSIBLE connection. Will clear codes again and start, warm up etc. I guess could be an O2 sensor but am getting no codes related or I don't know what values are supposed to be in the data readings. Again, no P codes, only these codes now (after clearing the original codes): 00A016 (inst. cluster), and 000401 and "engine control fault" on the console. Thanks for everyone's help and input.
It’s starting to sound like it may be a defective ECU or bad ground. But a bad ECU ground woud trigger tons of errors including undervoltage errors and reset errors.
(All fuel, air, spark components etc are heavily monitored, so with no errors related….. its pointing me to something electrical.)
Can you list which ECU’s had which codes. In a list format? It’s important to know the ecu. If i had to guess then its likely an Engine ECU failure. An error will trigger the surrounding “unaffected” ECU’s to go into limp mode as well, so focus on the ECU with the memory errors.
So there are direct errors pointing to specific issues, and then there are “symptom” errors that are just point to other ECU’s that forced the limp mode.
Wiggle the fuses and any wiring that you were previously working on, to see if one of them has intermittent contact.
Last edited by 991Targa4S; 02-11-2022 at 07:24 PM.
It’s starting to sound like it may be a defective ECU or bad ground. But a bad ECU ground woud trigger tons of errors including undervoltage errors and reset errors.
(All fuel, air, spark components etc are heavily monitored, so with no errors related….. its pointing me to something electrical.)
Can you list which ECU’s had which codes. In a list format? It’s important to know the ecu. If i had to guess then its likely an Engine ECU failure. An error will trigger the surrounding “unaffected” ECU’s to go into limp mode as well, so focus on the ECU with the memory errors.
So there are direct errors pointing to specific issues, and then there are “symptom” errors that are just point to other ECU’s that forced the limp mode.
Wiggle the fuses and any wiring that you were previously working on, to see if one of them has intermittent contact.
I don't see anything on the data for the iCarsoft that tells me about which ECU it would be. How many ECU's does a 2017 991.2 C2S have (engine and PDK and)? I am including the screen shots that I am getting on the tool that don't look normal. Everything else is consistent. The weird thing is, I switched plugs and coil packs between cylinders 2 and 3 and it is still showing 2 OK (N/A) and 3 roughness but no misfire!
I don't see anything on the data for the iCarsoft that tells me about which ECU it would be. How many ECU's does a 2017 991.2 C2S have (engine and PDK and)? I am including the screen shots that I am getting on the tool that don't look normal. Everything else is consistent. The weird thing is, I switched plugs and coil packs between cylinders 2 and 3 and it is still showing 2 OK (N/A) and 3 roughness but no misfire!
There’s quite a few ECU’s that belong to Body, Chassis, & Powertrain functions. Theres also multiple communication networks as well.
For reference, heres a pic from 991.1.
991.2 wouldn’t be too much different but it won’t be exactly the same.
I have to read through your thread again. What led up the the first time this happened. Any work done to the car?
The engine ECU interprets the oscillation of engine speed (or smoothness of engine speed) as an indication of misfire. If the engine speed is not smooth, the engine ECU will interpret it as rough meaning the driver will feel vibration but it will not damage the engine or catalyst because these are not actual misfire but combustion that are not happening well.
If the engine speed is really not smooth, not only the driver will feel it more but you could have actual misfire (i.e. fuel is not combusted and dumped to the exhaust) which may cause engine or exhaust damage. It is usually not a big issue to have misfire at idle because the exhaust temperature and flow are low so you won’t damage anything. But if you have misfire when the engine is loaded, then you could damage your engine or your catalyst due to higher exhaust temperature.
So are you saying that if you move the ignition coil which is initially in cylinder 2 to cylinder 3, the roughness follows the ignition coil? If yes, then you have found your culprit and it’s this specific ignition coil.
I would make A-B-A coils swaps on cylinder 3 and 5 which shows roughness.
A: ignition coil of a cylinder which does not exhibit roughness
B : ignition coils of a cylinder which exhibits roughness
the ABA will confirm to you that the problem is with the coil.
For the other cylinders where N/A is displayed for the roughness, I would assume the ECU did not enter the conditions to monitor the smoothness of the engine speed. So maybe you need to drive the car more and idle it so that all engine adaptations are carried out.
A good thing to make sure to the misfire adaptation is to keep the gearbox in N, vehicle stopped, rev the engine speed to 6000rpm (engine hot of course) and let the engine speed go back to idle by itself.
Please also note that every time you erase the faults in the engine ECU, you may reset engine or misfire adaptations so you must drive the car again and re-adapt the engine before letting it idle and check for presence of roughness or misfire code.
I would make A-B-A coils swaps on cylinder 3 and 5 which shows roughness.
A: ignition coil of a cylinder which does not exhibit roughness
B : ignition coils of a cylinder which exhibits roughness
the ABA will confirm to you that the problem is with the coil.
For the other cylinders where N/A is displayed for the roughness, I would assume the ECU did not enter the conditions to monitor the smoothness of the engine speed. So maybe you need to drive the car more and idle it so that all engine adaptations are carried out.
A good thing to make sure to the misfire adaptation is to keep the gearbox in N, vehicle stopped, rev the engine speed to 6000rpm (engine hot of course) and let the engine speed go back to idle by itself.
Please also note that every time you erase the faults in the engine ECU, you may reset engine or misfire adaptations so you must drive the car again and re-adapt the engine before letting it idle and check for presence of roughness or misfire code.
Good stuff, thanks. Have kept track of cleared codes and next drives, that's what I meant by consistent codes. Will try your suggestions Only concern is, it's running pretty rough and I don't want to cause further damage. Have had quite a bit of idle but not in N. Thinking of pulling the coils and bench testing. Anyone know which terminals/blades should be tested for resistance? BTW, old plugs (less than 10k miles) looked great (only switched because Porsche says to), can use those for replacements if needed for eliminating new plug issues.
The engine ECU interprets the oscillation of engine speed (or smoothness of engine speed) as an indication of misfire. If the engine speed is not smooth, the engine ECU will interpret it as rough meaning the driver will feel vibration but it will not damage the engine or catalyst because these are not actual misfire but combustion that are not happening well.
If the engine speed is really not smooth, not only the driver will feel it more but you could have actual misfire (i.e. fuel is not combusted and dumped to the exhaust) which may cause engine or exhaust damage. It is usually not a big issue to have misfire at idle because the exhaust temperature and flow are low so you won’t damage anything. But if you have misfire when the engine is loaded, then you could damage your engine or your catalyst due to higher exhaust temperature.
So are you saying that if you move the ignition coil which is initially in cylinder 2 to cylinder 3, the roughness follows the ignition coil? If yes, then you have found your culprit and it’s this specific ignition coil.
No, I would have expected to follow the coil but it didn't.
There’s quite a few ECU’s that belong to Body, Chassis, & Powertrain functions. Theres also multiple communication networks as well.
For reference, heres a pic from 991.1.
991.2 wouldn’t be too much different but it won’t be exactly the same.
I have to read through your thread again. What led up the the first time this happened. Any work done to the car?
Here the info:
At 9931 miles on the my 2017 991.2 C2 (and just over a month off of warranty), I did a spark plug change, oil change, brake fluid flush and air filter change. Yesterday, after putting about 35 miles on the car, I did some "spirited driving" in Sport Plus on a remote local road thru the hills not far from my house. As I arrived at the rural highway that leads home, the check engine light came on and the multi-function display read "Engine Control Fault, Consult with Shop, Driving Permitted". The car felt and sounded like it was misfiring. Shortly, I saw a PSM warning flash and the PSM "off" light on the console lit up (I have never driven with that off). That didn't last long and those items went away and it was back to the previous warning (driving permitted). In a short while, the warning changed again to "PDK Trans overheating, reduce engine load" so I pulled over and shut off the car. From the time the warnings started, I drove between 30 and 50 MPH as there was heavy traffic. After sitting a few minutes deciding what to do (late Friday afternoon), I restarted it and the original warning came back on "driving permitted" so I started off again. After another 1/2 mile, the misfiring seemed worse so, even though I was only about a mile from home, I decided to pull over and call for a tow. I had it towed to my house hoping I could use my iCarsoft to diagnose and repair it myself. I did the diagnostics today and one of the faults is 007010 "check engine control unit fault memory content". From my research and the way the car was driving, I am thinking MAYBE it is a bad ECU. There is also a PDK TCU but I don't know if it would have caused the misfiring symptoms. I cannot see any reason it would be related to the spark plug change but am open to thoughts about that. Also, I cannot find a stock ECU replacement online, only upgraded and/or tuned ones. ANY input is welcome, I'm not sure if I trust my ECU evaluation so am considering taking it to a shop (ugh!). I also got codes of 00A008 "PSM failure", 00A016 "check engine" but not all the codes I found begin with a letter and my iCarsoft OBD is not giving me options to explain them. It only wants to see a letter, followed by 4 letters or digits.
02-10-2022, 05:16 PM
