I bought a used 2013 Accord EX-L 4cyl (2.4 i-VTEC) around July of this year; 1 owner, lots of good maintenance records, seemed like a well maintained vehicle; bought it w/ only 70k miles on it. 2 weeks ago I noticed the oil light came on for a split second (like it flashed 2 times, like a quick strobe). I was close to home and it had gone back off, so I drove it about 3-4 miles home. After checking the oil, the stick was bone dry! It took about 3qts to get to normal. The following week my “oil Minder” light came on; even though it has 3/4 fresh oil in it, I went ahead and gave it a full oil change (w/ the filter, etc).

Last week (~half a week after the oil change) while driving home the service engine light came on and started flashing, as the car went into limp mode! After checking codes, it was coming up with p0304 - cyl4 misfire. After looking at it the next day it showed 0304 and again added p0354 - primary or secondary winding problem in ignition coil D (also 4th cyl)- so I assumed it’s likely electrical in nature (but saw that other cylinder issues could still show this code; is that correct?) After dinner clear coffees and troubleshooting, I was only seeing 0304 unless I was unplugging the coil during testing.

I first bought a new spark plug, and swapped the coil with another cylinder to rule that out. The original plug in cylinder 4 didn’t seem that bad (assuming it was an original plug w/~80k? miles). The new plug and coil swap did not fix or change the problem. I’m the meantime I put the old plug back in so I can hopefully make use of the $30 new plug after it’s fixed! I did notice on the new plug apparent oil on the plug (which confirms why I lost 3qts of oil so quickly; the valve cover is seeping but there is otherwise no leaks).

I then took it to a mechanic shop for further analysis, but it appears now like he doesn’t want to get too deep into the engine!; he has been nice and working with me “to kept the cost down” (by not opening the engine), but he’s telling me now that if I open the engine I’m going to be into the 3k+ range to get it repaired… I think he is also having an issue with one of his main mechanics being out sick, or otherwise not showing up for work; and trying to not take on long/hard jobs because if it).

In the meantime, he did do a compression test and found that the 1st 3 cylinders were ~200psi, and #4 was~ 90-100.

At my request (rather, after I inquired about it), he did a cylinder soak using the bmw equivalent of the ac Delco x66p (he initially said he doesn’t usually do that stuff, but then recommended I get him a bottle of it before digging deeper into the engine after results of the compression test)

Now, after the soak, cyl4 dropped from 90 to 75psi! I thought it’s supposed to go higher after the cylinder soak! Would that be indicative of what the issue could be?

I don’t know if he did a leak down test yet.

I was originally expecting the likelihood of a stuck valve, and I thought he initially said that would cost like $1-2k but now he’s saying that if he removes the head it would need to be sent to a machine shop to be repaired and end up costing > 3k; I was always under the impression that is only really necessary if it has been warped or cracked (usually sure to being overheated); but “if” it is a bad / stuck valve, shouldn’t it be much easier to fix at the repair shop?

Based on the above info, is there any “likely” causes left of my problem, and what are reasonable rates for parts/labor to repair the likely / possible causes of my issue?? Thanks in advance!