Hi, I have a 30v 2.8 A4 and after replacing my spark plugs, wires, and the ignition coils I am still getting a p0300 random multiple misfire with a flashing check engine light. I replaced the plugs & wires about 1,000 miles ago because I was hoping that would take care of it, it did for about 300 miles then a solid CEL came back. So I scanned it and was getting a p0300 code and a bank 2 catalyst deficiency code, that I'm guessing was caused by the misfire. I then replaced the ignition coils and still had the same codes, about 20 miles after replacing the coils, I got the flashing CEL back. I cleared the codes and only get the p0300 multiple misfire code when the CEL comes on. I searched and can't find an answer to this issue, does anyone know what could be causing this? could it be the wiring to the ignition coils?

I also tried putting my old coils on and I got a p1393 power output stage 1 code, and it ran worse than it ever had, so I swapped it back and cleared the codes, and i'm just back the p0300

also while replacing the coils one of the new spark plug wires broke so I put an old one back on.

 

What plugs and what did you gap them at? Ever replace your coolant temp sensor? Clean your MAF? Ever change your front O2 sensors? How many miles on the car?

 

16684/P0300/000768
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Contents [hide]
1 16684/P0300/000768 - Random/Multiple Cylinder Misfire Detected
1.1 Possible Causes
1.2 Possible Solutions
1.3 Special Notes

16684/P0300/000768 - Random/Multiple Cylinder Misfire Detected
Possible Causes
Air Intake System leaking
Fuel Supply faulty
Injector(s) faulty
Ignition Cable(s) and/or Spark Plug(s) faulty
Ignition Coil(s) faulty
Exhaust Gas Recirculation (EGR) Valve (N18) stuck/open
Camshaft Position Sensor (G40) faulty
Possible Solutions
Check Misfire Recognition
Check Air Intake System
Check Fuel Supply
Check Injector(s) and Injector Sealing
Check Ignition Cable(s) and Spark Plug(s)
Check Ignition Coil(s)
Check Exhaust Gas Recirculation (EGR) Valve (N18)
Check Camshaft Position Sensor (G40)
Special Notes
This DTC indicates that one or multiple cylinders are misfiring, but the ECU fails to identify the cylinder.
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I just used cheapo autolite $1-2 plugs and gapped them at .63mm like the book says. I actually just replaced them after I made this thread and it took care of the issue. who knows how long it will last this time though.

 

Sounds like a faulty ICM (Ignition Control Module) had the same issue with my car and there was always a misfire on that cylinder

 

Okay well the random multiple misfire p0300 is gone but I am still pulling a code and CEL from the catalyst deficiency I believe the code is p0430. The car runs fine until you are driving a constant speed, say 50mph then coast or decelerate (like if someone in front of you is turning off etc.) and accelerate again it will stumble and clunk. Does this sound like a bad or dirty Catalytic converter or an O2 sensor?

 

sounds like a clogged cat. go under the car and hit the cat with the soft side of your fist. if you hear rattling, your cat needs to be replace. i used to have bad rear 02 sensors but never got any problem driving the car. the clunk could also be bad engine and tranny mounts though. if you have a 5 speed, does your shift move around a lot when you accel or decel?

 

Well, I went under the car and hit the cats and there was no rattling, the car is a Tiptronic, I wish it was a 5 speed. I cleared the code and it hasn't come back YET, It drives normally again, but as usual once it comes back you'll notice the issue.