View Full Version : 1999 3.0 mpg sudden drop
10-06-2007, 08:44 PM
I got a 1999 3.0 flex fuel that had its mpg have a sudden drop. I went from 18-19 mpg with normal gas to 14-15. and from 14-15 with E-85 to 12-13. I play around it both fuels frequintly thats how i know what i get for both. All i have done is recently i straight piped it but went through 2 tanks before i noticed the sudden drop. I allways thought losing the muffler would increase its power and economy but is it possible that the 99 3.0 needs the back pressure from the muffler? Even then i wonder why i went through 2 tanks fine.
10-07-2007, 03:02 AM
your exhaust is unlikely to be the culprit if all you did was replace the muffler with a patch pipe.
have you checked tire pressure, air filter, brakes (especially the rears)...ect.
as usual, try having codes pulled even if the cel isnt on.
10-07-2007, 08:14 PM
well i have had some screeching from my front wheels for some time now. I have ignored it because it started after i had my rotors replaced and thought it normal at first. it continued on and i continued to ignore it because i couldnt find any signs of rubbing at all.
Other then that i read the 3.0 likes to get better gas around 3rpms, sense i got the stright pipe ive been keeping the car around 2rpms, im gona try keeping it around 3rpms for a tank and see if that makes a difference.
10-07-2007, 09:20 PM
It could make a big difference.....for whatever reason ford made the torque peak of most vulcans around 3600 rpm.
10-08-2007, 02:51 AM
while that is true, i dont think thats your problem. even at 2,000 rpm i still get 20-21 mpg highway, 24-25 if i run around 3k.
brake noise is never normal. if your front brakes are dragging for some reason, this would explain your sudden drop.
10-27-2007, 07:13 PM
i have a 99 3.0 and when i got it fuel mileage was at 14-15 i work at firestone did fuel system cleaner (some people say it BS. now i don't). and a fuel filter and went up to around 18-19.
10-27-2007, 09:00 PM
its appeared have gone back up with some change to driving habit and different wheel size. Now at 17-18 with regular gas.
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