If anyone wants, I can get into further detail about swapping the 2.5L in or replacing the engine in general, but there are plenty of posts here on the forum about installing an engine. A few notes: This engine already had a recent AOS and water pump replacement. I opted not to do the IMS/RMS. They looked good with no leaks and as a 1997 engine it has a dual row bearing. Given the history of this engine, I expect some other failure before the IMS goes. It had a failed water pump when I first got it and I flushed water through the cooling system after removing it from the 2000 S and before installing it in this car. I am still not sure that all the coolant passages are clear.
My wife recorded video of it's first drive with the replacement engine. It ran rough at idle when I first started it, but smoothed out above 2,000 rpm. I knew it could be minor and simple, or a sign of impending doom. For an engine that sat abandoned under a tarp in my driveway for two years, I call running at all a big win.
Video:
https://youtu.be/QkheUt0eRUs
Using an Autel MD802 showed codes for a misfire on 2 and 5. Troubleshooting, I started by replacing the coil and plug in 5. That cleared it. With 2, I tried the coil first. -Still a misfire. I swapped in a plug and it cleared. All the plugs are old, and I'm not sure why those two were bad. I'm going to replace them all with new ones later. With the misfires cleared, it was smooth except for a quick surge at idle. That got better and went away as the ECU adapted to the 2.5L engine.
Now that its a running, driving car, I can get a look at all the other problems. A quick list from my first drive included: The washer fluid tank leaks, Brake wear light is on, Airbag light is on because I disconnected the SRS while my grandson rides with me, Steering wheel is canted about 15 degrees when the car is straight (Alignment seems good, so I'm guessing the wheel was not set when it was aligned.), Typical old Boxster issue of windows not quite operating right when the doors close, Heat shield on the exhaust rattling, and more. Nothing serious, but lots of little things, common for a 18 year old car that has seen a lapse of care.
I'm driving it daily to work this week. I'll probably fix some of the minor issues in the evenings. My only big concern right now is the issue the engine had before with cooling. I have smelled some coolant when I parked it, and the coolant level has changed as I have driven it. It may be fine, since I didn't really take the time to purge the air out of the system after refilling. I've been driving with the tank vent open to allow the air out of the system. I'll see how it progresses and flush/replace the coolant in about a week.
Next, I want to start focusing on the actual Challenge car and V8 swap. The work on the '01 has been a good warm up and refresher. It will also be a back-up car for the Challenge if I run into problems or bust the budget with the other car.