Long time lurker, first time poster, usually my questions are resolved by just searching. I'm at a crossroads now. I got my 2014 SHO non-PP back in January with 25k on it. It's been flawless up until now (32k miles or so) with just performing normal maintenance. Took the car to the in-laws yesterday for Father's Day celebrations. It's about 75 miles one way, had zero issues on the way. Fueled up, had to take the longer way home due to a road closure, but cruised back at 55-60 on some winding country roads home with no issues, and merged back onto the Interstate heading home. Guy in a minivan in front of me was trying to merge onto the highway at 40, so I gave the SHO about 75% throttle to go around and noticed some hesitation when passing. The MIL began to flash and the car had a definite miss. I pulled over, restarted, but the same result. I was only about 10 miles from home so I limped my way back on back roads only accelerating very slowly and parked in my driveway. Loaded up Torque Pro and scanned to find P0301 as a trouble code and P0087 as a pending code. Restarting the car is more difficult now (5-7 seconds of cranking before fire, occasionally longer) and it still has the miss.
When turning the car on the fuel rail pressure spikes to about 100psi and settles around 35-45psi. Once it cranks and idles it seems to hover around 180-220, but it's not stable. (I've got videos if it helps.) There's a definite fuel smell when it's idling rough, my guess is the injector spray pattern is crap, perhaps due to low fuel pressure, and it's not burning properly. The HPFP is noisy, but I don't know if it's noisier than it should be as I never had the engine cover and the sound proofing material off of it with it running before.
The car is out of warranty because it's a salvage car. It had fresh water flood water inside of it, but not even high enough to even damage the seats, no water was in the engine, and I doubt it was high enough to affect the in-tank pump and certainly not high enough to damage the HPFP. I really don't think this is residual damage from that's just coming up 7,000 miles later. It's not my first salvage or flood car, and probably won't be my last. Haha.
I'm trying to repair this myself, leaning toward the HPFP, but before I drop $300+ on one, I wanted to know if there's a better way to diagnose besides towing to the dealer. Our dealer here is notorious for charging full list for everything and every diagnostic fee and labor hour possible. I only got misfire on one cylinder which makes me think maybe injector, but unsure why that would cause low fuel pressure unless it was just stuck open. I've also read other folks having LPFP problems, but when powering on the car the rail primes to 100psi or so. I've also seem a few mentions of the fuel control module, but I don't know if there's shade-tree diagnostic method for that. I did just fill up 75-85 miles before the issue, bad gas could be a possibility, but it took an hour of solid driving before any issues appeared and I think it would've happened sooner.
Is there's a service manual available somewhere inexpensively where there's troubleshooting steps available, or specs on what fuel pressure is supposed to be during various phases of prime, start-up, idle, running?
Any advice is much appreciated. I sure miss driving the SHO every day. Oh, and the car is bone stock.