Need help with a couple things.

[reesea17]

I posted a topic a while ago about my S4's recent drop in fuel economy, which is still a problem. Most have offered up the solutions of changing the EGT sensors, the O2 sensors, and the MAF sensor. I have also seen a couple different posts that leaks with the vacuum tubes can cause economy issues as well. I can't seem to find much information on how one would go about upgrading and replacing the vacuum tubes and was wondering if someone here would be able to help me out. Also, my S4 is getting to the point where it needs its second timing belt change and I am wondering if this could have anything to do with the loss in fuel economy as well. Does anyone have any additional items they think could cause a loss in fuel economy? Mine is currently pretty bad, and by bad I mean I average around 13-15 mpg city in a mostly stock S4, nothing really done to it except for the dar-intake mod. I used to get around 19-22 mpg city.

[Peter Badore]

Bad coolant temperature sensor could be making the engine run rich most or all the time.