6.1183 MPG......any help would be appreciated

Welll fellas, as the title states, I'm having some fuel efficiency issues. I got 72.9 miles out of 11.915 gallons which calculates out to 6.1183 MPG. Last take I got around 14 mpg all city. There didnt seem to be anything abnormal about it ran this tank.

98, 199000 miles, 99 intake, 4.5 inch lift, 31s, stock gearing (3.55), apn header, custome downpipe, IAT sensor relocation.

During this last tank, it did finally snow so we played in that a bit but shouldnt have affected it that much. I know that variable aside from my rig could have affected it, such as Cold temperatures and possibly the switch to winter fuel. I cant for the life of me figure out why it would have dropped so dramatically. I do have a heavy black ring around a four week old tailpipe so I know Im running rich. I plan on moving the IAT sensor back so that doesnt fool the computer to thinking that the intake air is colder than it really is when it gets pulled into the engine. Im also in the process of building a MAP sensor adjuster. How common are fuel leaks,whether in the tank, lines or fuel injection? How would one eliminate that as a possiblity? Fuel Pressure and leakdown test? Where would be a common place to find fuel leakage of some sort? Cap rotor and wires were changed about a year ago. Plugs werent to much earlier than that.

Ill have access to my garage once I head home from school so Im going to start tryin to diagnose the problem/s, but any pointers would definately help me out.

Thanks Guys

Jeremy

Replace upstream O2 sensor

Done about 6 months ago, but its possible its bad again. I may need to test it somehow. Luckily its still under warranty.

Oh, forgot to mention,, no check engine light but I havent checked for stored codes.

I'd be looking at a locking gas cap.

I could be an evap system leak. The rubber hose transition from hard line to the tank is what im talking about. I had to replace mine recently as it developed a tear and was reporting about 8 mpg.

Very simple fix. My mpg went back up to 13 as soon as it was repaired.

cal said:

I'd be looking at a locking gas cap.

Click to expand...

haha could be true..

I didnt even consider that it may have got syphoned.

Something in my tank or nearby it gurgles pretty good for a few minutes when I stop. Ill look at those lines as soon as I get down into my garage. Thanks! Any other pointers?

Would regearing help any? idk

crooked barrel said:

Would regearing help any? idk

Click to expand...

.

Of course but its not going to fix that issue. 31s and 3.55s are very livable. You need to do a tune up and check for major issues.

Maybe a simple check, but if just one of the injectors is damp after driving, change them. Helped my fuel mileage tons, but mine is an older Jeep. Most parts stores also sell just the o-rings for injectors.

my .02atriot:

I know that I need to regear but I should be able to get pretty good with stocks and 31's. I was getting 14 a while back and that was even with signs of running rich.

I havent noticed any fuel leaking from the orings, but I suspect that it it would have to be a fair amount to not have it evaporate faster than it can surface, especially when hot. Ill probably replace the orings just to be safe anyway, Ive had the fuel rail off so many times in the last year or so for manifolds and gaskets and such that ive probably done some damage. Good pointer. Thank you.

You need to work on your math skills You can't get more accuracy out than the lowest accuracy number going in.

As far as the vehicle goes: Playing will always have an affect on fuel milage, especially if you go WOT a lot.

What kind of driving do you do? City in 4WD? Cold weather startup really sucks fuel, especially if it just sits getting warm.

What weight oil are you running? In cold I run 10-30W, but I think 5-30W is recomended for the nasty cold we have been getting lately.

Zuki-Ron said:

You need to work on your math skills You can't get more accuracy out than the lowest accuracy number going in.

Click to expand...

so 10 ÷ 3 ≠ 3.3333333333333333333333333333333....and so on....?

Just asking, maybe it's something new?

sjkimmel99 said:

so 10 ÷ 3 ≠ 3.3333333333333333333333333333333....and so on....?

Just asking, maybe it's something new?

Click to expand...

Significant Figures (aka Sig Figs). If you have 10.3 and 10.345, you can only be as accurate as the tenths place because that's your least accurate data.

As far as your mileage, My Jeep usually gets around 12-13mpg and it's the same setup as yours.

i would be looking at your relocated IAT sensor because that thinks it getting the air temp from inside the intake were the air would normally be warmer once the engine is warmed up and it's getting the freezing cold air from the outside and posssibalyl even some snow trown on it makeing your engine run richer to help it warm up

you said you finally got snow so i would imagine it's now colder only makeing the condition worse

i would think that and the combonation of "playing" in the snow would cause that kind of millage drop

playing in the snow really does suck gas lol

that might not even have anything to do with it that's just where i would start looking

-Dylan