OK. We can try this to get me some data.
You need a terminal program to access the COM port. Since Win7 doesn't have HyperTerminal you can use PuTTY.
Get it here and save it.
Open PuTTY from wherever you saved it and select the Serial button. In the tree list on the left at the very bottom is Serial, click it.
Now set the COM port setting there.
- Serial Line to connect to: COM4 (I think that's what you are using...?)
- Speed: 19200
- Data bites: 8
- Stop bits: 1
- Parity: None
- Flow Control: None
Again in the left menu tree click Logging under the Session item. For logging pick 'All session output' and Browse to a location to save the log file. Give it an appropriate name. Save.
In the left menu go to Session (at the top). Give this connection profile a name in the 'Saved Sessions' field and then click Save. Now we are ready...
Connect up the PLX to the computer and with the car running, click Open. A black terminal window should open and if there is data, gibberish should appear in it. Let it run for a minute or so (do a couple of throttle stabs) and then Close the window. Zip up the log file that you made and post it.
Hopefully I can get an idea of what's going on from the data stream from the PLX.