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small vacuum leak

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what would you assume would be a rough change in gas mileage with one some where relating to the hvac flap controls? i could usually get ~29-30 in practically the same driving as what i'm doing now in warm weather, .. my last tank i got 25.75 mpg... it's been getting into the 20's and the last few days the 10's at night, here highs of 30ish

i haven't been idling my car much at all to warm-up, maybe a total of 5 mins for the whole tank, of actually done on purpose.

side question, would a temp gauge reading of ~140 instead of 180 affect it much too? my temp gauge has been this way for several years though.

before i got this driving cycle my typical was 19-20 mpg when it's nice out, and sometimes high 16's when it got cold. this is a ~15+% hit and the new mileage figure is almost 15%.

and for you guys that have done work behind a dash for hvac reasons, any idea where the most likely culprit of a hose crack/leak would be? because of vacuum it makes it's self known best from 2K up to about 2.5K rpm....hisses pretty good. this leak mostly effects my ...damper?.. moves the output to heater when under medium high to high load.. like going up a hill in 3rd or 4th gear.

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how much vacuum line do you have on a 3.1? just replace it all.

since i can hear it in the cabin, i'm thinking it has to be inside... i don't know how much it is. you ever had this done? is it possible to do w/o taking most of the dash apart?

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It could actually be the controller itself if you're hearing it inside the cabin. In fact, I think it's a high probability that is the case.

I have approximately 17.362 miles of vacuum lines under the hood of my car. I'll be changing all of it out in the spring.

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It will not be the controller - the car is too new for that.

The HVAC systems on car from the era are almost entirely electronically controlled. Even the actuators are electric.

Follow the sound, and find the leak that way.

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