Engine will idle higher if the AC is engaged otherwise once the engine warms up the idle should settle ~650 rpms. FWIW I performed the OBDII scan test with the AC off, engine warm and idling. If the engine is idling high (ie: a change from normal) IME that can be one sign of a faulty TPS.
IME when my FZJ80 TPS went bad it started as an intermittent high idle (1100rpms after engine warmed up instead of ~650) with occasional bucking/hesitation as I was driving ~30-50mph, felt like the engine was misfiring or like a slug of water (bad gas) just went through the engine. At highway speeds it ran fine. Then the high idle became constant and dropped to around 950rpms, but still the intermittant bucking/hesitation continued at lower speeds.
So I hooked up a cheapo Scan tool that had some live data functions including TPS and went for a drive. As I drove down a level highway at a steady 45mph the TPS readout on the scan tool would bounce around at the same time as the bucking/hesitation, for example (not exact values) it might drop from 14.3 down to 0 then hunt around to 4.7, 8.3, 9.5, back down to 4.3, etc then level out back to 14, until next time it started bucking/hesitating.
Replacing the TPS and setting with the scan tool is fairly straight forward IME with one TIP: If you replace the TPS yourself make sure the lever on the back side of the TPS is clocked correctly ie: so the Throttle body lever will rotate the TPS (lever) when you press on the accelerator pedal. You need to open the Throttle a bit then push the TPS in place so the two levers engage each other. You'll know you have it right because when you let go of the Throttle it will want to rotate the TPS ie: before you have the TPS tightened down. If you don't clock the TPS correctly you'll get no pedal response and the scan tool will show 0%.
HTHs
