Need some advice.

[OE24]

I have a 2014 Audi A4 S-Line 6SM. with 46,000 miles

Mods:
APR Stage 2 since 28,000 miles
APR turbo-back exhaust since 14,000 miles
Forged Billet DV since 14,000 miles
R8 Coil Packs since 35,000 miles
NGK R Platinum Spark Plugs gapped to 0.028 35,000 miles

All services have been done by Audi, all oil changes, everything.

Driving home one night from the grocery store, after a long 300 mile trip, car just randomly begins to shake. I was less than a mile away from home, and as I pulled up, CEL started flashing, EPC light was on, thinking to myself, definitely a misfire. So, I ran the codes and got P0303 (Misfire Cylinder 3). I pulled the coils, and then pulled the plugs.

On the plugs there was a little bit of oil on the plug itself, but no broken pieces or anything. I bought new plugs, gapped them to 0.028. Same issue, car is still misfiring. I played with the coils by switching them around and the misfiring still remained in cylinder 3. I then checked resistivity of all coils, and they were all good.

The following day, I have it dropped off at Audi.

I call the following morning, and they said that cylinder 3 has no compression, I need a new engine and that they will not be covering anything due to my tune(this was expected).

Now, my question is...could this really be a mechanical issue, such as a failed piston ring, rod or piston itself? Meaning, could there be some other underlying issue to cause little to no compression in just cylinder 3?
I am getting the car back and taking it home. What else should I check before I tear down the head?

Could it be a clogged fuel injector just for that cylinder?

I am speechless that I need a new motor. I always babied the thing, it is garage kept, I kept up with all services and such. On top of that, I literally drove like 300 miles earlier that day,everything was great, and then go to the grocery store, and out of no where bam.

I must also say, that the car was not blowing any smoke out the tailpipes, just rough idle, and the dash lights (CEL/EPC).

[vwladz]

Most likely failed compression ring, I wouldve said that its a timing issue if your car wasnt 2014. Audi start putting updated timing chain tensioners in 2013 cars (still old design chain though), so its a little chance that you timing is off. Anyway, double check compression with local mechanic you trust, burnt exhaust valve is possible scenario too if car run lean. Picture of my A5 btw.

[turboqlars]

Most likely failed compression ring, I wouldve said that its a timing issue if your car wasnt 2014. Audi start putting updated timing chain tensioners in 2013 cars (still old design chain though), so its a little chance that you timing is off. Anyway, double check compression with local mechanic you trust, burnt exhaust valve is possible scenario too if car run lean. Picture of my A5 btw.

Of topic, but what happen whit sylinder no 1 on your A5? And why?


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