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Cylinder 3 Misfire At Idle

N

NSchultz7

Ready to race!
Location
N/A
Car(s)
2020 Turbo Blue S4
Experiencing some issues with my 2020 A3. Car is tuned stage 1. 20k miles. I recently found what was originally a soft code stored for cyl 3 misfire. It's since evolved into a solid CEL. Decided to look into it and found misfires only happen at idle (700ish RPM). I have no issues driving normally or even at WOT. The idle isn't particularly rough or lumpy. If the RPM is raised by putting the car into sport mode, pushing the accelerator slightly, or turning the AC on, misfiring stops. I moved both spark plug #3 and coil pack #3 to cylinder 4, but the misfire persisted in cylinder 3. I believe it's more prominent when the car is somewhat "cold". I reflashed my tune about 5-6 days ago and the misfires had stopped for awhile, but they just came back. At this point I'm lost. I've flashed back to stock for now, going to see if it happens on stock file. I imagine it will, as I was tuned for almost 2 years before any problems. Haven't driven it yet, but on initial logging at idle there are no misfires.

Not sure where to go from here. I'm kinda thinking injector, but not sure as I don't have problems while driving/WOT..
 
JerseyDrew77

JerseyDrew77

Autocross Champion
Location
Virginia & NC
Car(s)
2016 TR GTI S 6MT
NSchultz7 said:
Experiencing some issues with my 2020 A3. Car is tuned stage 1. 20k miles. I recently found what was originally a soft code stored for cyl 3 misfire. It's since evolved into a solid CEL. Decided to look into it and found misfires only happen at idle (700ish RPM). I have no issues driving normally or even at WOT. The idle isn't particularly rough or lumpy. If the RPM is raised by putting the car into sport mode, pushing the accelerator slightly, or turning the AC on, misfiring stops. I moved both spark plug #3 and coil pack #3 to cylinder 4, but the misfire persisted in cylinder 3. I believe it's more prominent when the car is somewhat "cold". I reflashed my tune about 5-6 days ago and the misfires had stopped for awhile, but they just came back. At this point I'm lost. I've flashed back to stock for now, going to see if it happens on stock file. I imagine it will, as I was tuned for almost 2 years before any problems. Haven't driven it yet, but on initial logging at idle there are no misfires.

Not sure where to go from here. I'm kinda thinking injector, but not sure as I don't have problems while driving/WOT..
Click to expand...
Since you already swapped the plugs and coils and the problem didn't follow, sounds like it's the injector. It might be slightly dirty/clogged so when your car is at an idle with low rpms it misfires but goes away when driving normal or at WOT. That's because more fuel is flowing versus when your car is sitting and the rpms are low, it doesn't require as much fuel. You can try some fuel injector cleaners like Berryman B-12 or Seafoam to see if that helps. If not, then replace the injector.
 
N

NSchultz7

Ready to race!
Location
N/A
Car(s)
2020 Turbo Blue S4
JerseyDrew77 said:
Since you already swapped the plugs and coils and the problem didn't follow, sounds like it's the injector. It might be slightly dirty/clogged so when your car is at an idle with low rpms it misfires but goes away when driving normal or at WOT. That's because more fuel is flowing versus when your car is sitting and the rpms are low, it doesn't require as much fuel. You can try some fuel injector cleaners like Berryman B-12 or Seafoam to see if that helps. If not, then replace the injector.
Click to expand...
I actually put some gumout regane high mileage in. Still working on getting through the tank however. This was after clearing the code initially. I noticed some carbon on the tips (they are normally pristine) so it's definitely cleaning something..
 
N

NSchultz7

Ready to race!
Location
N/A
Car(s)
2020 Turbo Blue S4
Diggs24 said:
Not always necessarily the injector. Since it is at cold start it could be the evap system dumping too much fuel into the pcv.
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How would one fix this? I read through that thread before posting as well as multiple idle misfire threads. I noticed you had mentioned unplugging the EVAP connector to see if that does anything.

Also, why would I be getting consistent misfires and then when I reflashed my tune, they went away for a few days?
 
N

NSchultz7

Ready to race!
Location
N/A
Car(s)
2020 Turbo Blue S4
Since I just reflashed to stock, I'm not currently getting any misfires. I'll have to wait until I am in order to test if unplugging the EVAP connector will help anything.
 
N

NSchultz7

Ready to race!
Location
N/A
Car(s)
2020 Turbo Blue S4
Sorry to be MIA, busy week. Doesn't matter the tune really as it's doing it on stock tune now as well :(
 
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