ok well i have a idle problem. it will be fine some times but others it will be at 1500 and surge up and down. other times it will just sit at 1500. only happens when the car is warmed up tho. but i checked the tps and its right on. but i disconnected the tps and the bac valve and it idles at 750 now but it will surge still up to 1500 and idle at 1000 but hen drop back to norm.
which leads me to believe it is the thermo wax. i dont know tho. looking for some input and what not. but if it is the thermo wax is it worth changing it or is it just esier to do the tb mod.
btw: s4

 

I'm having a similar problem, and I wonder if my thermowax pellet could be failing. All sensors are good on my car (88 SE), like you said.

I know you're not supposed to do it, but bump for more info.

James

 

i had an 87 turbo II with this type of problem, surging 1500 idle while warm, and it was the thermowax, it had not failed though...

it turned out the screw was not adjusted correctly!
so it was holding the throttle open slightly. try looking the FSM and finding how to adjust the therowax. theres somethign where your suspoed to adjust it inbetween the to marks on the therowax cam, so that it moves the right amount....

 

Theres a screw its your fast idle cam adjustment, the cam should be in between the two notches on the metal plate; you have to remove the tb and adjust it from the back, also be sure the tempuratures around 77 degrees F (room temp). If that doesn't work then its 80$ for the thermo wax at the dealer and be careful of the water-thermo vavle too if it goes out its 60$ and you'll shoot flames...