Another strange Idle question...

I have a 1990 xj auto trans. it starts fine. but once i let it idle it just slowly climbs the idle. after a minute or two it might be around 2k at idle then a little latter maybe idle at 3k. is this a faulty TPS sensor?

Check for vacuum leaks and retorque the bolts on the intake. This is exactly what mine did until I found two loose bolts near the fire wall on the intake. You can spray carb cleaner on the vacuum hoses while its running and if it stumbles, you've found a leak.

how about if i give it gas it cuts out. and almost sounds like a backfire unless i let off the gas then it stops.