ODB-II scanner to diagnose without a code?

Factual Questions
1

What can you tell me about consumer ODB-II readers? I see they have a lot of spread in their price range. Will a cheapie (generally) provide a reason for an event happening? Let’s say that my car started stalling this morning at idle after being warmed up. There’s no check engine light, other than momentarily during the stall. Or… are these things generally only useful if there’s a persistent check engine light?

I don’t mind spending about $100 (and if justified, a little more), but there’s a lot of appeal to only spending $40 or so, and I see them at close to $300. Of course, I could just take it to my mechanic (who I trust and have a good relationship with), but there’s also a lot of appeal to having a new, neat, toy, especially now that I’ve decided to try to keep the car for a million miles (really. I’m 10% of the way there), and things are bound to happen.

Any ideas/recommendations? (I think once the GQ has been answered, this latter question begs a move out of GQ).

(For what it’s worth, I’m convinced it’s a PCV-related problem, as I just had it replaced).

2

AFAIK, all the code scanner can do is to tell you the error code, and read sensor values. It’s up to the user to make the problem determination. Some are obvious (bad sensor readings), but others require personal experience.

3

That’s kind of what I’m looking into – will a “cheapie” give me the sensor values, or “only” a code (and only when there is a code)?

4

The cheapie that I have used only tells you if there are any active or pending codes. And of course, it has the option to clear them as well.

5

I’ve done some design work for these guys: http://www.autoenginuity.com/
Their system is about as sophisticated as amateur equipment gets.

6

Damn! That’s some fancy stuff, but beyond amateur pricing, I think! If my old Pontiac had ODB-II, though, I might reconsider just for being able to tune it!