Well Im thinking my TPS is stuffed but Im not sure so I'll ask for your generous advice.

I have an AU series II Wagon auto.
The problem is when Im driving and I start to coast... (ie: lift my foot of the go pedal to slow down ) the car seems to shift back to 3rd very noticably as if I manually shifted it. It also does this when Im crusing at say 90 or 100k's , it momentarially shifts back to 3rd and then to 4th again. Its like the car thinks Ive given it a bootful , but I havent. I took it to a auto mechanic and wouldnt you know it ! the car drove fine for him and it didnt show any fault codes either.
This problem is intermittent. Some days you drive and all is good, but then the next time it plays up.
Am I right assuming a TPS problem or do you think it may be something else.?

Your advice is much appreciated.

p.s. I have also noticed that when the car is in this "mood" it idles at around 1100rpm in neutral. But it returns to a normal idle when tha car is behaving itself.

Lock up torque converter is working. it disengages when the throttle is moved a bit. can be annoying sometimes. mine does aswell.

i don't know if there is anyway of adjusting it.

It is very noticable and is definately not normal
.
It is very noticable when coasting towards a corner for instance before braking.

Im noticing this only happens when it idles high, so I replaced the ISC but it didnt change anything. Could the TPS effect the idle like this, or could the inhibitor switch effect it aswell??

I recently had this same problem, but mine kicked down quite bad. It turned out to be the TPS then when that was fixed gearbox came up with a solenoid fault.

Well its` all fixed. It was the TPS.

hi my car does the same thing and i not very mechanical but wat does tps stand for or mean thanks

It stands for Throttle Position Sensor

ok thanks how hard wuld that be to fix or cost to fix

U could pick one up from a wreckeers for around 50 bucks or I think about $120 ish new. I didnt pay for mine , the car yard that I bought my car from paid for it new so Im not sure.