I am hoping that some of you can give me some input as to where to start
looking at this problem. I am getting poor gas mileage. To start off I
have a '01 4x2 QC with the 4.7 and an auto. I also have an LSD and
4-wheel ABS just to get all the info out there.
This problem has been going on for over a year when it had 9k on it. I
now have 26k. I used to get 14 to 15mpg around town and 20 to 21mpg on
the highway cruising at 75mph. I now get 11 mpg and 12mpg if I'm lucky
and 18 to 19 mpg on the highway at the same speeds. To make this
interesting this all started in the period of a week. I went to the
dealer for a minor problem and while there they flashed my computer with
an update. The next weekend (couple of days later) I changed my oil to
synthetic. The mileage drop maybe started happening when I left the
dealer or after the oil change not really sure but it was all under one
tank of gas.
I have since had it to the dealer several times and they have flashed my
computer every time along with new updates but to no avail. I have
changed my spark plugs, air filter, and cleaned the TB several times but
to no avail either. I did find when I changed my spark plugs that the
tube that runs from the PCV valve to the rear of the intake behind the
throttle body was not attached back there. I put it back on but it fits
so loose that it comes back off if you just touch it. Could this be a
problem? Could the PCV valve be a problem which btw the only place I can
get one for the 4.7 is the dealer.
The engine seems to run fine other than the pinging I have got ever
since that flash they did. I tried new plugs which helped but not
entirely. The only other thing I can think of is maybe the synthetic oil
isn't compatible. Not sure what to do but any suggestions and thoughts
would be helpful.
Jeff Durling
Systems Administrator
(954) 741-9742
jdurling@wdci-telecom.com
www.wdci-telecom.com
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