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2000 grand cherokee mpg issues i6

6K views 41 replies 15 participants last post by  rchinsp 
#1 ·
hey ive had my jeep for about 4 months got the I6 and it runs great and all but my mpg is horrible like 10 mpg and i have to fill it up alot and i dont have any leaks and my computer says 200 miles to empty everytime i fill it up and i replaced my fuel filter today and sea foamed it and now it says 260 miles to empty im very shocked haha i dont really trust the computer but how can i fix my gas mileage theres something wrong thank you
 
#3 ·
For future reference, you might wanna try out this revolutionary tactic of punctuating your sentences.

Now to get to the issue. Is this a new issue, as in you've been getting better mileage and all of the sudden it plummeted, or have you always been getting extremely low mileage?

Ignore the computer completely, its useless. Get your MPG calculations by hand, as its the only reliable way to find out what you're actually getting. Is the 10mpg by hand or by EVIC (the computer)?

How many miles are you sitting on? Have you kept up with maintenance (mainly the O2 sensors is what I'm getting at here)? Do you drive like a pissed off teenager? That will have the most effect is just how you drive it.

Since you just replaced the filter today, I would fill the tank tonight and then again in a couple days from now to actually find out what mileage you're getting. Do it by hand. In case you don't know how to do so:

1: Fill tank completely
2: Reset trip odometer
3. Go about your business for a couple days
4. Refill tank completely again
5. Divide number of miles driven (from your trip odometer) by number of gallons put in, boom there you go.
6. Rinse, lather, repeat.
 
#4 ·
replace air filter or upgrade air intake.
keep tires at proper pressure.
COAST to a stop, dont stop short. if you see a red light coming, just let off the gas and coast as long as you can before you need to brake, but GRADUALLY brake. i see all these fools braking super hard at redlights all the time.

when taking off from a red light, dont SPEED, but get to the highest gear possible, as fast as possible...without being a danger to the other drivers.
on that note, always try to drive in your highest gear.

do a real fuel system cleaning. sea foam is great for what you pay, but a real system cleaning is what you need.
just...dont do it at jiffy lube. i dont trust anything they do.

use the oil the manufacturer recommends.

use cruise control at all given oppurtunities.

decrease vehicle weight where possible.

change spark plugs (i hear e3 works good, but i also hear their gimmicky)

fuel pump

buy lighter wheels

use nitorgen in your tires instead of air

thats all i got right now, i know im missing something
 
#5 ·
i bought it not too long ago, and it has always got bad mpg and my tank is full of right now and im in the process of calculating it. nothings dragging i havnt checked my tires yet but. im thinking about installing new spark plugs how much would they run me and could i install them myself
 
#6 ·
not sure how much e3 costs but alot of people swear by the cheap ones at autozone/walmart
think their like 4 bucks a piece? or am i time traveling right now.
and on the i6 their pretty easy to do yourself, just becareful. they can get stuck sometimes and your going to probably get angry with it, and pull at it with channel locks and tear the boot and or wire....
patience is key, which is what i dont have.

anyways, spark plugs can be either really cheap or really expensive, just depends on if you want gimmick or economic.
 
#8 ·
NEVER use the E3 plugs in the WJ! You WILL get all sorts of misfires and possibly burn out the ignition coil. OEM champion copper core (or NGK for the few that had those OEM) is the way to go. Gimmicks will never pay off, especially on spark plugs.

Same goes for the nitrogen tire fills. The nitrogen won't cause any damage like the E3 plugs will, but you may as well just throw 40 bucks in the garbage disposal.
 
#11 ·
first and foremost, assuming your referring to the jeep in your profile, lets start with the obvious,

1. how many miles on the motor?
2. what size are your tires? stock size or over-sized?
3. check engine light? and history codes?
4. What did the previous owner say about the maintenance? did you ask for records?
 
#12 ·
E3 spark plugs are a complete and total gimmick and waste, you'll create all sorts of problems with them. Go look through your local auto parts store's flyers, one of them is always running a special on spark plugs. You're looking for Champion Coppers. DO NOT let them upsell you on them, you want the plain jane copper plugs.

Don't waste your money on Nitrogen in your tires or on any sort of upgrades right now. In factory stock form, which means normal air in tires on OEM wheels, normal air box, etc, you should be getting at least 15mpg if not more.

Also, it just occurred to me to ask. What are your trips like? Aka how far from school/work/etc are you. Are your trips very short and non highway based? My girlfriend's 4 banger VW Beetle was rockin along at 10mpg for the summer because she was driving less than a mile at a time; the engine never had time to warm up and she never really took it above 30, it was all stop and go traffic. That could definitely affect your mileage in a big way. I notice when I don't drive to school (~25 miles round trip all highway) my mileage will be significantly lower the next time I fill up.
 
#16 ·
On a one mile trip, the Jeep may not even reach full operating temp. If that's the case, then a good bit of your driving is done with the engine cold and running rich while it attempts to warm up. That's going to take a massive toll on the mileage of any vehicle.
 
#21 ·
^^^^^^^:2thumbsup:

also thumbs up on the nitrogen coments

its the most rediculous thing i have ever heard of, your buying something that with your own tire inflation device, you can put in your tires all the time for free, and yet people pay for it??
Like selling bottled salt water on the beach.
 
#23 ·
Like selling bottled salt water on the beach.
or just bottled water in general :cheers2:
i think that was frances idea, trying to get one over on us dumb americans.

anyways sparkplugs are easy. especially on the I6 because the engine bays so much cleaner than a v8

if i remember, i may be mixing different vehicles together here (ive had quite a bit) BEFORE DOING ANYTHING. make sure you mark where each wire came from on the engine. you want them to plug into the same area. and dont forget to gap the new plugs. most autostores will do it for you, but id recommend getting the gap out of the owners manual, borrow their gap tool, nd doing it yourself. unless you trust the guy at the counter.
you have a cap and rotor. look for the circular cap with 7 wires coming out of it.
follow them to your spark plugs. now just yank them out (the back ones can be a pain, not much room back there) now very carefully, thread the new plugs in. i say careful because you dont want to cross thread them, or ding up the prong.
use a plug grease on them, and plug the wires back in! simple as that.

and ill reitterate, make sure the plugs go where they came from. i prefer to do them one at a time so theres no mix ups. unplug, install, plug in. move to next, same thing. :cheers:
good luck bro!

and like i said earlier, be careful with stuck wires. if you tear it, your going to be buying another, and typically they dont come cheap.
 
#17 ·
wyattwj123 said:
my work is like a mile away and i go there every day and also to friends house that are a few miles away and have to fill up every week
This is definitely a huge contribution to your bad mileage.
 
#19 ·
Champion copper. Do a tune up, make sure your tires are properly inflated. You can spend thousands of dollars improving gas mileage, but you will never make back the money you've saved.
 
#24 ·
No wires on the WJ. One ignition coil that sits across all six plugs, so it's impossible to switch the firing order around. The 4.0 WJ is probably one of the single easiest vehicles to replace plugs on, up there with I-4 japanese engines.

Plugs will have to be gapped at .035". Anti-seize on the threads, and dielectric grease on the top at the coil connection never hurts.
 
#27 ·
I have very similar profile. Work is one mile away but do 22 mile carpool run 2 or 3 days a week. I6, 4WD, 102k. Was getting 14mpg for months. Spent an hour or so in 4LO last weekend and now am getting 16mpg in town and 21-22 on the HWY! Guess something got freed up in the transfer cases.?!?
 
#28 ·
#30 ·
wyattwj123 said:
replace the spark plug cant really tell a diffrence but didnt really expect too lol but i already replaced my fuel filter cleaned the air filter went wheeling a little today
Wheeling will also kill your mileage, just a little FYI. Let us know what your next tank looks like, I'm curious what was causing it. If that stuff doesn't fix it, you gonna do the O2 sensors next?
 
#33 ·
I have been paying close attention. On the way to school for carpool I will see 14 mpg. This is from cold start to 11 miles in mix of hwy and traffic. I reset computer at school and have over 20 mpg showing when reverse trip is finished and I am at work. Seems like operating temp is important
 
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