Hello, I've been experiencing what's either injector trouble or a failing coilpack, but I'm having some determining which. When injectors in these cars fail, is it a soft failure or is it a hard, immediate failure? If it is normally a soft failure, do engine bay and/or fuel temperature effect how badly the injectors perform? Do these injectors tend to fail open or closed?

My car has had phantom misfires for a little while and yesterday it culminated in the car hitting what I'm assuming is a limp mode of some kind where it could barely make it up hills or even maintain 20 mph on flat ground. The phantom misfires all line up with what other forum members have reported (high load low rpm stumbling, gets worse on inclines, variety of trouble codes seen below, etc.). The CEL was flashing the whole time as well, but the car idled without issue, and the flashing CEL would stop the moment I stopped trying to apply throttle. Even when in neutral the car wouldn't rev past ~3k, and I saw AFRs spike to around 22:1 (perhaps this is caused by a soft fuel cut for limp mode?). I took a short video of it The only fault code present was a single pending P0301 cyl 1 misfire.

After letting it rest for a day, I started it up tonight to do some datalogging, and everything seems normal as far as AFRs are concerned while I was still getting a slight misfire, which kinda points towards coilpacks, but the lean condition with the flashing CEL and complete lack of power independent of RPM is kinda concerning. The pending P0301 code disappeared after tonight's datalogging session.

This is a whole bunch of codes that popped up last week during a rainstorm and some heavy misfiring. After searching for them on this forum, they all point towards coilpack failure (including the C1555 code). The pending codes other than P0718 all disappeared after a 40 minute drive without issues. I swapped out the relevant input shaft sensor for P0718 and in doing so had to remove the battery so all codes disappeared. P0718 hasn't come back since I replaced the sensor.
This is the result of my datalogging session tonight. You can see that the commanded and measured AFRs are pretty much identical other than when the ECU turns off the injectors at 0 throttle while moving. Sharp spikes in throttle position is to induce a misfire stumble as they seem to occur more frequently when jumping on the throttle after coming to a complete stop, especially up an incline.

As far as fixes go, the car has ~175k on what I'm assuming are OEM coils, so I've ordered a whole set of Hitachi IGC0073s. The sparkplugs are NGK Iridium IRs (one of two OEM sparkplug options) that were replaced about a year ago (15k miles ago), so when I replace the coils I'll retorque the sparkplugs just to make sure they haven't come loose. I'm planning on checking injectors as recommended and outlined by @cutsheal5 here.

I would really appreciate any information I may have missed or skipped over, especially regarding how limp mode works in these cars as that would explain the weird AFR reading I observed when the CEL was flashing.

Thank you much for reading through my long, rambling post!