First of all everyone seems to say that the JTS engine runs a little rough at idle.... but....
Your best bet would be to get a ELM327 connector (usb cable or bluetooth $10-20) and multiecuscan (diagnostic software - free
). It also allows you to monitor sensors which may give you some info if there is a faulty/slow sensor.
I have a similar problem to you at the moment except mine also hunts occasionally when idling.
Simple low cost things to check would be:
- Clean the lambda (O2) sensor connection plugs with electronic cleaner. You can also cut a little bit off the connection with the male pins for the pre-lambda sensors to provide a better fit. Or you can also solder them in place but I wouldn't do that until you know they're working A-OK. This seems to be problematic with this particular engine
- There are two big wiring connectors at the back of the engine by the firewall you can clean with electronic cleaner.
- Check lambda resistance using a multimeter (grey and black wires I believe). I found on my car they were different and that prompted me to take them out and check them - only to find one wasn't and original bosch lambda (ordered and new one immediately after running a few diagnostic tests
- Check the battery with multimeter for correct voltage if you have one. Clean all the battery terminal connections (sanding them with light sandpaper is an option for better connection).
If you are lucky it'll be that easy... but if it isn't:
- Wait for diagnostics software and spend a few hours checking sensors
- Clean MAF but be careful to not damage it (read a guide and use a cleaner that will not leave residue)
- Clean Throttle body (avoid moving the butterfly if possible - easiest way would be to remove and clean it).
After that it will probably come down to faulty lambda's, coils, crank sensor, MAF or injectors