I’ll try to sum everything up as well as i can, in sections. questions are welcome ofc! Sorry for the long text.
2013 S4, 157300 ish km (97600 miles), dual pulley tune with unitronic, then switched over to 034 3-4 months before the incident. Oil changed every 5000km (3100miles), owned the car since 137000km (85100 miles) IC bricks replaced at 145100k (90100 miles). Upper timing chain covers were leaking at the time. Battery is from august 2012. Stock cats that were on their way out (i know, bad idea on dp tune, i had JUST gotten my test pipes not long before this happened lmao)
June 8 2024: did an oil filter housing gasket replacement, a bit of coolant leaked off the front of the supercharger onto the front of the engine. When i started the car an hour or 2 later, there was a squealing noise that stopped after a few minutes, similar to a funky pulley bearing. I went on a test drive to my workplace thats 10mins drive away and on the way back, the car cut out mid drive. I rolled it down the bridge i was on and pulled off to the side, went to restart it and it started right up like nothing happened, no code or anything. It drove perfectly fine until the night of the incident, about 200-300km on and off, mainly city driving to school and work.
Night of June 13 2024: i was driving home from seeing my girlfriend, heavy rain, and all beforehand was great. Suddenly i got misfires on cylinder 2 and not long after, on cylinder 6 as well. I drove to the nearby audi dealership to check what was up. It was closed but i parked at the entrance and used my OBD11 to scan n see and all i had were misfire cyl 2,6 along with hide cylinder iirc. I also got out and the motor sounded fine other than the misfire, both at the front and at the rear, no metallic or clunky noises. I kept going carefully as i lived very close to the dealer i was at and not long after, the car just cut out, no warning nothing. This all happened within 3.5 km (2.2 miles) from when i got the cyl 2 misfire to the car cutting out. The engine temp was where it should be, coolant was topped off as well and oil on dipstick and MMI. No smoke and no noise as far as i could tell, although with the rain it was tough to hear. No obvious roughness from the motor either, other than the misfires and the related shaking. No leaks nothing on the ground either. I pulled off to the side again, like the first time and tried to restart, only this time it wouldnt spin over at all. I remember the electronics would cut in and out when i tried. A scan gave me one code: p3054, starter jammed or electrical malfunction. That was the only code. I called a friend with his 2017 sienna over and tried boosting by jumping from the front jump posts, same symptoms as before. To be fair, i didn’t leave it connected for a few minutes, i connected the jumper cables and immediately went to start it. I ended up towing the car to my house. I also remember seeing the battery voltage was down to 7-9 volts.
The week after: i tried diagnosing the car at home. I checked the usual stuff, spark plugs, oil filter, charging up the battery. Spark plugs looked good, i had replaced them at 143000km (88800 miles). I couldn’t get cyl 3’s plug because there was rubber from the old ignition coil sitting on top of the plug and i couldnt easily get my plug socket over it. Oil Filter looked good too, just dirty oil as expected from 5200km of driving, no sparkly bits in it. It did smell a bit of fuel tho, but a sample sent to blackstone labs later confirmed the oil was perfectly fine, no diluted fuel or coolant in it. No weirdness at all. For the battery, i left it on my charger for a bit and once it charged up a bit, i stuck it in my car and tried to spin the engine with the 5 plugs out. It did spin over for maybe 2 spins. I immediately stopped it and called my brother over from excitement. I put the plugs and coils back in and went to start it again. It spun over again for a split second before it abruptly stopped, and i checked the battery and it was down to 9 volts again iirc. We also tried boosting it by hooking up a known good range rover battery straight to the s4’s battery, no difference in symptoms. This was when the old battery was at 9 ish volts.
My parents wanted to get it towed to their general mechanic, not an audi expert. This is where the mess begins. They told me the engine was seized but i had my doubts. 1. They took the sc belt off but NOT the accessory belt, which was still on the car, yet they didnt give my sc belt back, it wasnt in the car either. 2. I doubt they even removed the spark plugs coz cyl n.3 still had the debris around it. If they removed it to spin it over, they wouldve taken that gunk out. 3. I found out later that 2 of the 8 crank bolts were partially undone. Makes me wonder if they used the proper crank tool to spin it over or if they tried to do some weird stuff to try n spin it. From there, we got it towed to my uncle’s place until we could further diagnose it, since we dont have space back at my house and my unc has. He also used to own a garage back in the day and still works on his own cars, he even owned a modified b5 a4 back in the late 2000s.
At my uncle’s place, my dad and i tried to spin over the engine by hand. I got the little socket that goes between the crank bolts and we tried to spin it over but it wouldnt budge. Here’s my doubts about this: 1. We still had the accessory belt on as well as the plug from cyl 3, as we were tight on time at the time. 2. I found out after we rounded the socket off that there were 2 screws poking out and not flush with the crank. 3. We dont have a breaker bar and ended up trying to turn it with a 1 foot long torque wrench. After this i got an oil sample to send to blackstone and the car sat for 10 months, until last week.
April 6 2025: i randomly had a thought session and immediately thought, with the battery’s age and how it died/ spun over later, i should’ve tried putting a good battery in it first. I went to grab my old battery and put it on the charger. It went from 4v to 12v over a day, and then 5 hours later it shot back down to 4v, so obv the battery is super dead, especially considering its been 10 months.
My next step is to get an oem battery from audi and to put it in. And see if it cranks or not.
Worst case scenario: bottom end is toast, as i’ve seen in many videos and forums.
Best case scenario: its just a battery with shorted cells and i’ve been overthinking all of it this entire time. Especially considering how i got misfires on opposing banks, unless both IC bricks blew at the same time lmao
What’s you guys’s opinion? Anyone with a similar experience? Any help is appreciated!
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