Chasing some smaller issues on it.
So the heater started to come back around on it. That's good. When I test drove it, I never thought to check the heater. First cold night with it, no heat. While the heater core may be a little plugged , I knew it was the blend door actuator based on code 25 out of the HVAC headunit. So I changed the blend door actuator and that now works.
Heat was still lukewarm at best. Did a coolant change on the car (standard maintenance, not trying to fix anything) and slowly but surely, I'm starting to get better heat out of it. The inlet and outlet temperature on the heater core when I'm not running the heat are closer together. So it's getting better flow. Almost to nuclear heat again when the engine is warm.
The big issue, and I think it's a combination of things, is it likes to throw a cylinder 5 misfire code idling, hot, in gear. When I test drove it, sounded like it cranked a bit funny but didn't think much of it. Figured it was a worn spot on the flexplate from having a lot of starts. However, I do think this has a weak cylinder. I don't believe it to be a head gasket - it's not using any coolant, no bubbling, no overheating, oil and coolant looked great. Obviously, as soon as I got it home, and before I Knew this was an issue, it got 8 new OEM ignition coils and Motorcraft plugs.
That combined with some other issue (it really wants to idle at 500 RPM, hot in gear) , it will throw a p0305 sitting in a drive thru or traffic. It will start to idle rough below 550 RPM and then it steadily drops to 500. Definitely not a dead miss, but I can feel it idling rough. It won't stall, either. If I turn on the AC or defrost, it will bump up idle to around 600 in gear and then it's fine.
Instead of doing a leakdown test and figuring out where the problem is, I'm just going to look for some vacuum leaks and possibly replace the IACv. It's definitely lazy. If I stop quick, it'll drop to about 400 RPM before it actually opens up. I have no clue how this engine can even aspirate at such a low RPM! If I can get the thing to idle at 570 or higher by eliminating , all will be well! I've debated doing a seafoam thinking maybe it's crud built up on a valve from a lot of city miles from grandma putting to church.
I loaded up the rear with weight for winter and quickly found myself on the bump stops. Bought some Moog Cargo coils for it and we're sitting level now!
Drove it on a few longer trips out to my parents. 25MPG. That's pretty solid! This is also the first vehicle I've had where the MPG display seems to be dead on with what I calculate by hand.