Stumped over crappy mileage
 

right now im gettin around 9-10MPG out of my 96 F150 w/ 302. I did a complete tuneup, new tps, new egr pressure sensor, new exhaust w/high flow cat, new o2 sensors and a seafoam treatment through a throttle body vacuum line. i still continue to get the same crappy mileage, babying it, or driving it hard. im stumped over this and would like to get it fixed. ive searched on here but tried almost everything ive found with no success. any ideas or suggestions are welcome.

Stoopid question- with the other mods, what size tires are you running on that truck?

30x9.5R with 3.55 gears...came with it when i bought it

Stock tire size it 235/75R15..... That's only .5 inch difference, im height. THe width is what is killing your mileage. Put stock tires on it, I bet you'll see a differance. Did you change, or clean the MAF meter?

Exactly what I've got on mine. 12/13 in town, 17/18 hwy, and we've got hills.

the tire size you have will not make that much difference, if you were running 33's i could see it! you might go over your vaccuum system, and check your EGR for leaks. this could cause your engine to run rich. recheck the EGR position sensor for proper installation. the computer relys on this for proper fuel metering! also recheck all your connections make sure no pins were pushed out ,(usually you would get a engine light) that is if your light works, assuming it does.

whats the best way to check the vacuum system for leaks besides feeling...also is it possible to install the egr pressure sensor wrong, if i remeber correctly it was a sensor with 2 rubber hoses coneection to the egr tube.

you EGR valve may be stuck open via trash &carbon build up...the computer cannot detect this!but it can detect the extra air comming in and compensate for it. thus causing your bad gas milage. make sure you put the 2 hoses back to the right ports... :-X22

What sort of driving do you do? A lot of short trips will hurt your mileage, especially in cold weather. Do you use the 10% ethanol? Switching to regular would probably gain you about 1 MPG. Have you tried a treatment of the fuel injector cleaner you add to your gas tank? This could help your mileage even if the engine seems to run smooth. I assume you changed the air filter. Just a few small suggestions.

i do mostly suburban driving, but my mileage should still be better then it is. right now i run Plus gas in it, a couple of days ago i did a sea foam treatment, with most of the can being dumped in the tank.

Are you burning any oil between changes? Could be from low compression.

Even with 35s and a heavy F-150 I've gotten 16 on the hwy before w/ my 302.

no burning oil...only thing gettin burnt is a hole through my wallet. i dont really know what else to do...im about to just park the truck.

Codes?
 

Have you pulled your codes to see what your buddy, the computer, thinks is wrong? I haven't seen any mention of that. Change the lube in your dfferential and your transmission as well as the transmission filter if an automatic. You've started to systematically find the culprit, keep on the trial.
Tex :-X22

You can check for leaks with a propane gas torch,UNLIT. Just introduce the gas into the system by cracking the gas valve and pass it around any possible areas for leaks. Your idle should change if you pass the gas by a leak.

:-X25

guzzler96

I know it sounds strang but I picked up 3 to 4 MPG when I changed my thermostat