Mercury

Car does not stall but idles too slowly when in gear, when radiator fan comes on, etc. car has had a recent complete tuneup and runs well other than this. i am not getting any codes back, check engine light is not on. i have replaced throttle body, iac, throttle position sensor, and egr sensors with used parts. no change. why is pcm not increasing my idle? thanks

I used to own a 1998 mercury mystique and had the same problem. it turned out that the carbon canisters and fuel filter had to be replaced. i would go ahead and change the filter, but wait and see if that helps before changing the canisters.