_alexparker18
03-12-2023, 03:03 AM
I’ve been having this issue since I bought the car in 2021 and I’ve been struggling to figure it out since then.
Some back story:
Shortly after purchasing the car and sitting in it running, the idle never felt quite right. It always seemingly hummed along at sub 1000 rpm as it should with an occasional bump ever 4-5 seconds. At this point there are no warning lights on the dash. A few months later while idling the car starts to misfire and goes into limp mode so I restarted the car and drove it to a shop to find a cylinder 4 misfire. Usual spark plug / ignition coil diagnosis was performed but the issue didn’t return with such severity to throw an engine light again. I later replaced all spark plugs and the cylinder 4 ignition coil in hopes of solving the issue.
The issue never went away and the strange idle has continued on and off for my entire ownership of the vehicle with seemingly no correlation to outside temperature, oil level, etc. and no check engine light present since the very first instance of recognized misfire and EPC warnings.
Lately on a cold start the idle will fall to 1000rpm or less and then back up to 1200 ish until it cold start procedure is over and for the first time since 2021 I am experiencing what feels like misfire followed by a 1200rpm idle surge after sitting in the car idling for extended periods of time (20-30 mins) with again no codes or check engine light present. The strange idle feeling is once again not consistent but it’s usually an indication that if I sit long enough I will experience the major rpm spikes and once the first spike occurs it usually will reoccur every 2-3 minutes of idling until I shut the car off with the issue then usually not returning until days or weeks later.
I recently had a decent oil leak from the oil filter housing fixed and heard about the secondary air valves combination being in close proximity (I think). I then learned the function and thought that if enough oil was leaking and interfering with the valves performance then the cause of the issue was officially pinpointed but after further research I found that any issues with these Valves including carbon build up have DTC codes associated with them so back to the drawing board I went.
I have taken it to my local shop specializing in euro vehicles but without being able to successfully replicate the issue or a DTC code relating to it they were unable to determine the cause.
Forgive me if the information on this issue is on this forum and I have missed it during my search but if anybody knows or has heard of this and can provide some insight please let me know.
Thank you.
2012 Audi A6 3.0T @ 90k miles.
Some back story:
Shortly after purchasing the car and sitting in it running, the idle never felt quite right. It always seemingly hummed along at sub 1000 rpm as it should with an occasional bump ever 4-5 seconds. At this point there are no warning lights on the dash. A few months later while idling the car starts to misfire and goes into limp mode so I restarted the car and drove it to a shop to find a cylinder 4 misfire. Usual spark plug / ignition coil diagnosis was performed but the issue didn’t return with such severity to throw an engine light again. I later replaced all spark plugs and the cylinder 4 ignition coil in hopes of solving the issue.
The issue never went away and the strange idle has continued on and off for my entire ownership of the vehicle with seemingly no correlation to outside temperature, oil level, etc. and no check engine light present since the very first instance of recognized misfire and EPC warnings.
Lately on a cold start the idle will fall to 1000rpm or less and then back up to 1200 ish until it cold start procedure is over and for the first time since 2021 I am experiencing what feels like misfire followed by a 1200rpm idle surge after sitting in the car idling for extended periods of time (20-30 mins) with again no codes or check engine light present. The strange idle feeling is once again not consistent but it’s usually an indication that if I sit long enough I will experience the major rpm spikes and once the first spike occurs it usually will reoccur every 2-3 minutes of idling until I shut the car off with the issue then usually not returning until days or weeks later.
I recently had a decent oil leak from the oil filter housing fixed and heard about the secondary air valves combination being in close proximity (I think). I then learned the function and thought that if enough oil was leaking and interfering with the valves performance then the cause of the issue was officially pinpointed but after further research I found that any issues with these Valves including carbon build up have DTC codes associated with them so back to the drawing board I went.
I have taken it to my local shop specializing in euro vehicles but without being able to successfully replicate the issue or a DTC code relating to it they were unable to determine the cause.
Forgive me if the information on this issue is on this forum and I have missed it during my search but if anybody knows or has heard of this and can provide some insight please let me know.
Thank you.
2012 Audi A6 3.0T @ 90k miles.