Well, Kaylee hasn't been quite as trouble-free as I thought... There has been a persistent oil smell in the cabin since I got home, and finding the source of that sent me down the rabbit-hole. On the drive home I didn't notice it at all, but I had spent an hour in the car with my mask on driving it from the airport with the salesman so I may have acclimated without noticing. Then of course, I picked up the old transmission, driveshaft, and rear end from the RX-7 to bring out to MI, so any oil smell was easily dismissed as coming from them.
However, that smell lingered for at least a month, and got me worried about something else burning oil. I couldn't find any signs of external leaks hitting the exhaust or manifold from the engine, trans, driveaxle boots etc, but there did seem to be very strong air pulsations out of the oil cap - more than enough to pop the cap off if it was sitting loosely on the fill hole. The pulsations seemed to line up with the frequency of one cylinder as well. Typically, this is due to high blow-by and possibly a failed PCV. A cold compression test gave about 140 - 145 psi across the board, so there weren't any stand-out cylinders - all were low. Hot compression was about 150-155, so a bit better, but the range for this engine is 134 - 192 psi so I'm still at the low end. Even more telling is that hot compression with a bit of oil poured into the cylinders to help the rings seal was around 180 psi. Well... crap. Not terrible, still within specs, but not great either.
Anyway, to try to get to the bottom of things, I picked up a cheap bore-scope that's basically a tiny camera & lights that plug into your phone for about $25. The quality so far is about as good as other bore-scopes that I've used, and the very stiff cable allows some ability to point it in a certain direction. Anyway, for the most part the bores looked good, with notable cross-hatching on all of them. The most wear that I could see was on the thrust-side of Cyl 3, where you can see a number of vertical lines, but none of them appeared very deep - I couldn't see any shadows but again it's hard to tell. In this picture, the piston top has some MMO on it since I had been soaking the engine for about a week to see if I could free up any stuck rings.
.
I also used some PB-blaster to soak the rings for a day or so, followed by an oil change to see if that'd help the rings seal any better. Changing the PCV required removing the intake manifold which was a bit of a task, with a few of the bolts requiring blindly feeling around with a combination of extensions through holes in the manifold. It was a four-hour job, with a lot of that from unfamiliarity.
Once I got down to the PCV it appeared to be working fine, and all the hoses and other connections were not blocked. There was a bit of oily residue on the inside of the manifold and ports, but that's expected with EGR and the PCV connected. The intake and cylinders got sea-foamed shortly after reassembly to try to clean things up, and the MAF and throttle were cleaned independently.
All the time she's been driving fine, and I haven't noticed any changes in performance from the driver's seat. I did a bunch of cleaning in the interior (it was already very clean, with the carpets appearing almost new and only a couple minor stains on some of the seats). For a while, you couldn't smell much over the vinegar and lemon smells, but baking soda sprinkled on the seats and left in an open container seems to be absorbing most of the smells. So far, the oil smell seems to have mostly gone away, but I haven't driven Kaylee very far since then or done much highway driving. All the cleaning and soaking of the rings seem to have helped a little - the compression pressure increased another 5 psi or so since the last warm test, so we'll see how things go on that front. Worst-case scenario, new engines for these are $500 - $700, so that'll probably be the way I'd go for minimal down-time instead of rebuilding and reinstalling the current engine.
Otherwise, two of the tires are pretty worn, and one of the ones that still had a bit of tread depth just developed a nice sidewall bubble, so it's time to get a set of 17" summer wheels & tires, with the OEM 16" wheels pulling winter duty. I got a set of 17" x 7" OEM Mazda 6 wheels for $80, and one of them was cracked so a good junkyard replacement was $50, so $130 for the new set. A few cans of paint later, and...
It's a bronze/gunmetal color that should hide dirt and brake dust pretty well. I kind-of wanted to go with a brighter gold, but couldn't find a specific color that I liked. The greens that I've been using for the RX-8 and the Saab before would clash terribly with the red paint, so those were out. The tires that came on the wheels are shot, so new tires are getting installed later this week (and I didn't bother to mask the old ones since they were getting tossed anyway).
