'93 Legacy - auto trans. has been shifting strangely at low speeds (i.e. throttle barely open) and the car just recently started throwing the idle switch fault code #42- I cleared the code and checked the TPS setting, which seems fine, but the code returns within a few days. What I really want to know is if these two problems (trans. and idle switch) could be related or are most likely separate. Is it worth taking the car to a shop that might be able to more accurately check the TPS and idle switch setting - or just get a good throttle body from a wrecker? Thanks.

Idle switch i think has to do more with the IAC motor. The TPS would defanitly throw off the transmission. It is uses as a subsitute for throttle pressure that the auto tranny needs to see in order to time shifts.

 

nipper

Yes the TPS/idle switch could be causing you issues with the shifting.

 

Check the TPS/idle switch

http://www.main.experiencetherave.com:8080/subaru_manual_scans/FSM_Scans/TPS_testing3.jpg