stangrookie302

So. I have a 93, lx, conv, 5.0L and I am having some interesting problems with my gas mileage. Upgrades: Cold Air intake from bbk, one inch spacer for throttle body, 3/8" spacer for intake plenum, bbk 70mm MAF 19lbs, stock exhaust up to the mufflers and they are flowmasters with duel chambers 40 series with 2 3/4" tail pipes. Underdrive pulley kit. So here is the interesting part. I used to get about 210-230 miles to a 13 gallon tank. Some days I get 170-190 miles to a tank. I have replaced my MAP sensor, carbon box, PCV valve, my vacuum hoses are good. If I take off my neg. battery cable off and let it sit for a bit 5-10 min. And then put it back on and drive for about 30 min, I get the better gas mileage until I have to fill up. When I fill up then I get worse gas mileage. If I take off the battery cables to "reset" my computer is that helping? Remember I am a rookie at this....

mattdel

Well, first off you're driving the wrong type of car if you're looking for mileage.
That said, EGR systems are quite capable of providing the difference in mileage that you're getting.
Do a seafoam treatment with the throttle held @ 1900 rpm.

stangrookie302

Well, I'm not looking for like 30 but I was gettin around 19 to 20 in town and about 24 on the freeway 5th gear. I forgot to mention 273 gears. I can't wait to upgrade to 373's. But at any rate, when I go from 230 miles to a 13 gallon tank down to 170ish, i get worried.

mattdel

Nothing that can't be explained by a few extra hard launches. You'll blow through a whole tank in about 60 miles if you keep your foot into it. Measuring MPG in these cars is really a science beyond monitoring the trip odometer.

stangrookie302

Understood.

reldla1996

Have you tried reading the codes from your computer? You probably should be getting in the 17-20 mpg range, with everything operating correctly, which lines up with what you've stated.

1998 t/a

did you ever consider the fact that you might have a leak in your gas tank? My DD town and country had one and I never noticed until I was filling up and noticed a steady dripping when its filled up

Tony71502

Cam, longtubes, 3.73s, and no EGR I got 22 mpg from Pittsburgh to Daytona and back. Lots of city driving and full throttles mixed in there.

Why do u have such a big MAF and is it calibrated for 19 lb injectors or were you stating that you had 19 lb injectors.

stangrookie302

Okay peeps, everything is fine. I was able to replace some vacuum lines that were clogged apparently and now that my PCV was replaced along with the hose and the new vacuum lines are replaced, I'm back to my normal MPG. It only took 4 freakin years. I have a BBK calibrated 19 lb injector MAF that is 70 mm and I have stock injectors which are 19 lbs. I got that info from other forums. I would instal a bbk 70 mm throttle body w/ a EGR spacer but California says no... stupid EPA. oh along with new exhaust from the block back but..... no. So everything right now is fine for my MPG, untill something else breaks. Just turned 150,000 miles on it last week as well. Thanks for the input felas.