Yes, VERY hard to track down. Has me about banging my head against the wall. Even on this older basic car!
No on the check engine light.
On the engine mounts, when you put it in drive, I can watch the engine shift noticeably and then when you put it back in drive, it shifts back. I thought this was the rear engine mount so I replaced that one and it didn’t seem to make any difference in the shifting or the rough idle. I can replace the other two (passenger side and transmission) as the car is 15+ yrs old and 120k miles if there is a chance that would do it. But that doesn’t seem linked because the idle in Park as started getting a little rougher now. But maybe that is even more of an indication they need to be replaced.
Haven’t checked the fuel pressure. What’s the easiest way to do that, some sort of inline gauge? Did change the fuel filter but that was about in there. When I rebuild the engine, I didn’t do much with the injectors other than a cursory inspection and replaced the seals. Gas mileage seems to be going down a little. Think I was up about 33 or so on the highway, now about 31ish, but could be the driving more than the car itself.
Haven’t really looked for vacuum leaks, but that is something I should do.