Intermittent stalling/rough running

For the past month+ our daughter has been having intermittent problems with her '08 Honda Fit(automatic), where it will stumble from a stop, and in one instance died.

At least a couple times it's happened within a block or two of it first being started, either in the morning, or after work. Other times it's happened during her ~20-minute commute on surface streets, after the car was warmed up. It happens nearly every day or 2. There have been no codes so far. 

We took it to our mechanic a couple weeks ago. He didn't find any specific problems, but ran a bottle of fuel injector cleaner through it & cleaned the throttle body. That made no difference. 

I drove it last night & it was running great, of course...

Any ideas?

Are there any relatively cheap OBDII data loggers out there, and if so, do you think I'd be able to see any problems since it's not throwing any codes?

In reply to tremm :

Thanks!

I spent a bunch of time searching the web yesterday & all the results were plugs -> coils -> maybe valve adjustment. The plugs & coils were replaced in her previous Fit last spring, then pulled from it after it was totaled at the end of May...but that doesn't necessarily mean they're still good. 

So I ordered a cheap set of coils from eBay yesterday, and if the plugs look bad when I pull them, I'll pick up a set locally. 

It sure sounds like something intermittent. Which would likely eliminate valve adjustment   
 

boy that sounds like a frustrating problem.  Can't wait to hear what the problem is