2001 SAAB 9-5 Throttle return spring too low force

Sorry to say no spring repairs possibly, what u have is your throttle body unit going bad, the next stage will be p1231 or p1230 code been set, which only repair is to replace unit, this stage is what is call unit been in [LIMP HOME MODE] when that happens u first have to clear codes then replace throttle body unit, start looking for a throttle body unit, price from dealer $568.80, or check goldwingsaab. Com, good luck

Is there ny chance of re-building the existing throttle body unit?

Non that I know of off hand, try using google search, u may get lucky & find somewhere that does.

"I bit the bullet" and purchased a new throttle unit at the SAAB dealer. Two different mechanics told me that you spray something on it to clean it there is to many electric components and you will begin to get all kinds of DTC codes. They were right. New one works great@ $522.00 including new "O" rings from the dealer w/12 month warranty.