Question about 1999 Saab 9-5
Looks like a classic idle air control IAC problem. The ECU should normally enrich (prolong the injection cycle) if load is put on the engine such as engaging drive or putting input to the power steering. It can only do this if it knows that the throttle is fully closed according to signals from the throttle position sensor on the throttle shaft end (see the outside of the throttle body at opposite end to the rotary accelerator linkage). The ECU then allows air passed the closed throttle plate> This is doen by two possible ways 1) a motor in the TPS eases the throttle plate open just a fraction or 2) a port on the side wall in front of the throttle plate is connected via an opened IAC valve to an exit port. If it is the valve type, just ensure that everything is clean by using carb. choke spray or WD40 and cloth/brush to remove oily carbon build up. Ensure the valve can open and close freely. If the TPS motor type ensure that everything is very clean and that any micro switch associated with sending 'throttle closed' signal to the ECU is also clean and able to click freely. AS a final measure check all the vacuum lines to the inlet manifold for any leaks, ingress of un-metered air needs to be ruled out as another potential problem source.
Posted on Aug 24, 2010
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Posted on Jan 02, 2017
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