Should I hear a single "click" at the Throttle Position Sensor when I open the throttle like I do w/ my 240? How would I test that TPS? thanks!

 

Yes, Its is supposed to do that click when you open it gently. You can adjust the TPS by loosening the tcrews that hold it and then rotate it slowly untill you hear that click and then tighten it there and check for that click when you briefly open the throttle again.
This will hold good only if your TPS is good. You can run the resistance check on TPS using multimeter.
BTW, Any symptoms that make you ffel that its not working correctly?

 

Update since I posted that question: was erratic idle, now NO-start:
I began having an erratic idle about a month ago after cold rainstorm. Idle would swing from high to medium-high, w/ an occasional drop to medium-low (maybe 400-500 rpm). Never stalled once. Acceleration was 100%. If I let it idle for 3-4 min, it indicated fault code 1-1-3 (short term fuel mixture too weak). If I cleared code and just drove (no idle) there was no fault code even after 30+ minutes driving. At the time, Brickboard friends suggested vacuum leak. I checked vacuum tree as well as I could (not exhaustive search) and didn't find anything. Having the good fortune of another Volvo to drive, I put it on back burner until today.

After more than a week sitting, I charged the battery (has 80% full tank). It made an odd sound when cranking, not the "rrr-rrr-rrr" (no gas) or "click-click-click" (dead battery) that we associate w/ many no-starts ... just a weak almost buzzing sound from engine bay. 5 minutes later, though, seemed to come closer to cranking but definitely not sputtering.
I can't help but think the 2 problems are related. Any ideas? Would it run strong w/ great acceleration w/ an ignition problem?

 

If yopu parked the car running at the last moment, i would expect it to strt again. Your lifters might have gone dry. i have read many times that in this case, Having a fully charged batttery and cranking the engine for about 1-2 minutes with throttle floored will give it a life. this is just and idea from what I have read here and have worked for people many times.
Other then that the next question would be the tune up? when was it done last. Did you try cleaning the idle motor for the rough idling problem?

 

It's not due for a tune-up but I guess I should pull the plugs, rotor, etc and at least take a look at them. I'll probably replace any those today in hopes of an easy fix. I haven't cleaned idle motor but would that cause a no-start?

 

Idle control motor will not contribute much to No-Start so you dont have to worry about it at first place.