real bad gas milage im stumped

[booo66]

96 xlt cont trac 4dr 129,000 ..4.0
ive done everything i can think of... cleaned maf, throttle body, new air filter, new pcv, new fuel pump (needed), new fuel filter, new egr sensor , new bosch oil filter, went to mobile 1 syn (0-30) oil , 1 sea foam through the pcv and 1 in the tank , 2 or 3 gas treatments, stock tires to 45 psi (50 psi on the tire wall) (30-9.5 futera) they look pretty aggressive though...and 7 days ago new motorcraft plugs and wires (old autolite plugs looked great but were gaped at 44 ...new ones I gaped at 54) trans fluid looks and smells good (i dont know the history of the trans ive only had it about 8 weeks but it feels good) brakes dont seem to be hanging up ..... AND IM ONLY GETTING 12 MPG I THINK I LOST 1 MPG SINCE I DID EVERYTHING........... WHAT THE FLOCK IS GOING ON HERE ............it runs great now and i dont do that much hwy driving but this sucks for a v-6 ........I had a 91 before this with almost 300,000 on the clock and ran like **** but I was getting 14 mpg....... with the same type of driving ..cold starts kids to school, trips to the store etc...ive got no codes but the only thing i can think of is o2 sensors if so whitch one or is this the best im going to get here in chicago in the winter...........HELP is it the tires or something else........................

 

[eXcali]

I live just south of chicago, and 14mpg was my average with mostly country roads this winter(55-65mph). The 30x9.5 will give you a little decline due to being about 1.25 inches taller and a little wider than stock. As for your O2 sensors if they were bad I'd think it would throw a code. The cold weather doesn't help either, if you have access to a code scanner try pulling codes just incase the CEL light is compromised etc.

 

[booo66]

Hi thanks
I was thinking I busted my hands up for nothing and i was thinking of buying a set of mich or dunlop touring 235/75/15 for the spring and summer and keeping the the other ones for winter do you think its worth the 300-400 bucks
thanks nick

 

[quedoggiedog]

noticed the smell of raw gas coming from my 1999 Explorer, and after looking under the hood I found where it is leaking. Almost directly under where the spark plug wires connect at the top of the engine, there is a white plastic looking piece threaded into the block and has wires connected to it. Does anybody have any idea what this is?? I didn't want to turn the truck into a fireball, so I'm not driving it but need to fix asap. I don't see how it could have loosened itself & I'm not sure that just tightening it back down will fix it. ANY IDEAS? ? ?

 

[booo66]

oh i very rarely get above 40 or 45 mph unless i jump all over it .....out of the 220 miles per tank only maybe 50 or 60 are hwy miles

 

[corkey]

after all them tune up parts , there is one thing you can do,,
disconnect the battery for about 5 minutes, and let the computer relearn all the parameters again,, it should get better,, i have a 96 xl, 4.0, and on the highway i get about 23 mpg, but i cannot give a city number, i have no traffic lights , or short streets,,

 

[booo66]

there should not be anything plastic that has anything to do with fuel so i dont know what to tell ya with out some more info
nick

 

[booo66]

i thought the same thing but my buddy told me mulitple starts would do the same thing but strange thing is i had to replace the pos battery connect 3 days ago and 2 days ago i put 5 gal in and ive already got 25 miles on the clock and it has barley moved but these gages are funny all of sudden it wikk drop to DEAD E so will see
thanks

 

[eXcali]

Good idea corky, I thought I posted that but think the antivirus scan restart requirement cut my message short. I don't know so much about doing multiple starts doing the same thing. The idea is the computer has to adjust the fuel richness and other adjustments based on engine wear etc. If you have a good enuff scan tool it can show you the different fuel trims and such to let you know if it's out of factory tollerances, I'd do this before forking out $100 worth of parts when it might not even be the problem.

 

[my98nnj]

Honestly, 12 mpg all local driving in the winter months isn't that bad.
I get about the same. On a trip I get upwards of 20-22.

I don't think you have a problem.

 

[corkey]

it might need a highway trip to get the computer to see that , start and stop is not all it does,, i know with just starting and going to work all week for me (a 2 mile round trip), will make the Ex very tough on the gas guage,, ,i know it sounds funny , but the old go for a drive on sunday , is not that bad a thing,, it makes the computer readjust the fuel trim for highway , and uses alot less gas , but that also carries over to the way the computer seems to work when it is used in town too ,

 

[tripplec]

I found that driving slow is not the best solution. The MPG to get can and usually goes up as you drive faster (to a point and depending on head winds if they are there). My reasoning is there is a sweet spot or zone. Typically the engine is running at about 2k whether at 45 or 55 there is little change and going faster you're covering more distance while the engine runs and uses the same gas. Hench more MPG. In more stop and go and grades OD seems to give better results on the 4.0, a bit more RPM and less load. We run with OD off in the city especially. The X seem very very sensitive to trottle pressure, a slight increase and the MPG drop noticalbitly. I have Jeep Grand and the results are better but OD off works for it as well.

How I know this is that I use a Scanguage. It connects to the computer and monitors what it senses calculating MPG amongst other things. You can tailor your drive habits and gearing better and see what situation cause MPG to drop to single digits. Heavy throttle and starting from stop puts the engine in the single digits for a while (can't do much about starting from a stop though). I recently changed the PCV and it helped the milage. It was original still.

 

[chrystal]

Here in the UK just did a 400mile trip on motorways and got 23.5 MPG....just cleaned maf and put in a new IAC

 

[corkey]

okay, i did a long trip with my Ex a bit ago,
i went to SMORR from my house,, a bit more than 1000 miles each way, on the way down there i got about 20 mpg,, using 91 octane, as it is so much cheaper south of the border,
but,,,,

and that is a big but, on the way home i was avaraging about 22 - 24 mpg , it seemed the more i drove on the highway the better it got till it could not get any better , again using 91 octane,,