Out of nowhere (car has run beyond perfect for 14 months) I noticed a miss, a lag, or a loss of power under slight load in the upper gears. I would liken it to a surge at low RPM under load, but idle and boost seems to be fine with full power being present.

Since there's no codes and I have done all the proper 60K mile maintenance, it could be a million things and rather than checking each of them to no avail, I was wondering if there was a way to log data white driving through the OBD port and into my Iphone, and then I could do my own research to fin the problem. If there is a way, what is the best software/hardware i should check out?

Cheers, and thanks for the help.

 

I believe there is software - I personally use a Matco Determinator to gather and record all live OBDII data. If I had to take a guess you might have an intermitient misfiring coil. You can test each coil on the vehicle at idle with a COP tester. This would at least rule out the coils at idle/low RPM's.

 

Certainly the data can be recorded. No idea whether an iPhone has such software.

Unless you get jag-specific software (such IDS or AE) you can only get a few items per second so don't record many on each trial.

You may be able to confirm a miss by looking at O2 sensors. It would be good to see it happening. I'd also look at Load since there are cases where the coils suffer, in case one is to blame.

COP test may well be worth doing. (So might checking the plug wells for contaminants.)

The PCM may be seeing the trouble but not consistently enough to flag codes. You have an advantage (your own sensors such as ears)

You're right that it could be any of a fairly wide set of things