[modern] Sources of Poor Gas Mileage

Since we have so many new list members and Eliot Brenner is suffering
from poor gas mileage I thought I would recap my vacuum leak post.

ANY vacuum leak will degrade performance. Now that I have plugged my 6
leaks and my car runs wonderfully in hot or cold weather. You CT people
recall we have had -10 to 105 F. temperatures the past year.

Here were my leaks:

  1. Both broken vacuum line "T"s off the top of the intake manifold.
    White PEP Boys replacements.

  2. Both worn out vacuum switches at Fuel recovery system (EVAP) under
    front driver side cowling under front bumper. $110 OEM only.

  3. Fallen off vacuum feed under intake manifold by throttle body. (This
    is a touchy feelly search with thin hands)

  4. Disconnected vacuum lines in climate control systems

  5. Center dash vent flap leak. (Yes the one you have to take out the
    dash. (yes I can repost that too.)). $65 OEM kit. 6+ hours of my labor.

  6. EGR valve vacuum leak. ($55 new part is only option, sorry no Chevy

Current mileage, City=13-16mpg, Highway (65mph)=23-26mpg.
I have Brett’s Sport Mode modification on about 50% of the time.

I will have to replace the intake manifold gasket to cut the last leak.
Fortunately, I spew so much gunk from my high mileage valves that I no
longer clean out the intake manifold as this clogs the gasket leaks.-----
Oh yes, last night entering the highway, Ford Excersion tries to out run
me as I merge. Another ignorant SUV driver. Damm does the “Mistress”
leap forward even at 65 mph!

Christoph Hanau
1990 XJ40 (US) 138K “The Mistress”