what am i missing for better mpg?

[rightaway]

i have a 93 zj 5.2. all stock. 140,000 miles. i'm only getting 11 mpg. this is what i have done so far for better mpg.nothing changed mpgs

new front 02 sensor
intake gasket replaced
new spark plugs
fuel filter
pcv valve
air filter
bg fuel injection service
trans service
diff services

i have looked around and most people are getting 13-17 mpgs. what am i missing or what should i look for?

[SirFuego]

Removing lead from your right foot?

[ddeadserious]

http://www.mallcrawlin.com/forum/showthread.php?t=18331

[rightaway]

i drive mostly highway. 25-30 miles daily. only 55-60mph. so i'm not driving it hard. i have hand calculate mt milage and its about 10.8 to 11.3.

[gcjeeping]

#12. A Honda Accord.

[hkszx2]

Wrong vehicle/ hobby for mpg worries

[ddeadserious]

I don't think this is a "How can I get better mpg" thread, but moreso, "What's wrong with my Jeep that's causing me to get such shitty mileage?". If X amount of people on so many forums are getting 14-20MPG, and he's getting 10, something is obviously wrong.

[DJJordache]

Wrong vehicle/ hobby for mpg worries

true

I don't think this is a "How can I get better mpg" thread, but moreso, "What's wrong with my Jeep that's causing me to get such shitty mileage?". If X amount of people on so many forums are getting 14-20MPG, and he's getting 10, something is obviously wrong.

true also....
how about looking for excessive weak on the ignition cap and rotor, take apart and clean the throttle body, check the engine block thermometer sensor (not the one for the gauge) maybe it is not getting into closed loop and running in open loop thinking the engine is too cool

[hkszx2]

This may seem like a dumb solution , and Im not trying to pick or make fun , but did you gap your plugs correctly when you installed them ?

[rightaway]

I don't think this is a "How can I get better mpg" thread, but moreso, "What's wrong with my Jeep that's causing me to get such shitty mileage?". If X amount of people on so many forums are getting 14-20MPG, and he's getting 10, something is obviously wrong.

thanks. that is what i am thinking.


this is my second car. i have a 94 g20 that i drive most of the time. but i like to drive the jeep better.

how do you check for excessive weak on the ignition cap and rotor?

i checked the gap twice before i installed them when i did the intake manifold gasket.

and how do you check for engine block thermometer sensor?

[paulkeith]

old clogged cat?

[Goosed76]

check cap/rotor for corrosion or signs of wear. clean throttle body. make sure it's reaching operating temp and entering closed loop. a cracked exhaust manifold would tell the o2 sensors its running lean and richen the mixture, hurting fuel mileage- but i would hope you looked at that with the intake manifold off. If it's not running up to par(I assume it's running ok though) a compression test wouldn't hurt, but doubt it's really necessary at this point.

[rightaway]

my milage has been like this for about a year now. i have cleaned out the the throttle body. i will check out exhaust manifolds and cap/rotor this week. i did check it all out when i did the intake manifold but didnt see anything but i'll check closer this time. everything seems to run find. not running issues at all. in the past 6 months i have also replaced

rad
water pump
thermostat
coolant hose
front brakes
calipers
rotors
brake hoses
oil pressure switch when i did the intake

[Goosed76]

what RPM are you running at highway speed?

[onegoodmason]

First things to check are obvious jeep things , the plenum gasket for starters . either visually inspect it or check out this TSB : http://dodgeram.info/tsb/2000/09-05-00.htm . Vacumn leaks , the jeep has all plastic lines , one small hard to see crack can reduce gas mileage . I`d check the vacumn , and consider new rubber lines , they are very cheap . Spark plugs , were you a good boy and bought the dealer Champions ? Tsk tsk , we all must learn , and so did I . I gained 3-4 MPG`s by installing NGK FR5`s , I think # 7252 . Slightly longer , and it even idles smoother . WELL WORTH the $2.81 each I paid , I bet I saved that in the first 2 tanks , NO , I`m not kidding either . the old plugs were dealer Champions , just what it called for , installed brand new in May 08 , when replaced they had maybe 5-7k on them . A good plug is good , but , if it`s not being fed , it`s no better than anything else , I`d recomend a good coil , I like my MSD .
With all you`ve done , you should be getting better than posted MPG`s . That`s right where I was before the new plugs , 10 mpg , but with a very heavy foot , 5" of lift and running 32X11.5`s , since the plugs , I`m getting 14-15 average and if I`m really nice and stay between 55-60mph , I can average 17-20 , that`s a hell of an improvement over the 12-13 HWY I was getting before .

My 14-15 isn`t bad for what and how I drive , I could do better , but where`s the fun in that !!

[rightaway]

First things to check are obvious jeep things , the plenum gasket for starters . either visually inspect it or check out this TSB : http://dodgeram.info/tsb/2000/09-05-00.htm . Vacumn leaks , the jeep has all plastic lines , one small hard to see crack can reduce gas mileage . I`d check the vacumn , and consider new rubber lines , they are very cheap . Spark plugs , were you a good boy and bought the dealer Champions ? Tsk tsk , we all must learn , and so did I . I gained 3-4 MPG`s by installing NGK FR5`s , I think # 7252 . Slightly longer , and it even idles smoother . WELL WORTH the $2.81 each I paid , I bet I saved that in the first 2 tanks , NO , I`m not kidding either . the old plugs were dealer Champions , just what it called for , installed brand new in May 08 , when replaced they had maybe 5-7k on them . A good plug is good , but , if it`s not being fed , it`s no better than anything else , I`d recomend a good coil , I like my MSD .
With all you`ve done , you should be getting better than posted MPG`s . That`s right where I was before the new plugs , 10 mpg , but with a very heavy foot , 5" of lift and running 32X11.5`s , since the plugs , I`m getting 14-15 average and if I`m really nice and stay between 55-60mph , I can average 17-20 , that`s a hell of an improvement over the 12-13 HWY I was getting before .

My 14-15 isn`t bad for what and how I drive , I could do better , but where`s the fun in that !!

i did put in champions or autolites but not ngks. i will try that. i did also replace the intake manifold gasket but i still have the stock cap rotor wires coil. where did you buy your plugs and coil at? do you think i should replace the cap rotor wires? is the aftermarket better than stock?

[onegoodmason]

go for the plugs , gimme a second or 2 afterthis post to confirm that # , those plugs are the "bomb" for the 5.2 .
As for the rest , I`d get the MSD coil , after the plugs if felt needed , the wires are fine unless you have a miss and will carry the power no issue . If you get the MSD coil after , you`ll be better off to re-gap your plugs 5 thou over stock too .
These plugs should be available at your local parts store , the coil too , but maybe a perf. parts store would have it in stock , as was my case . I`m in Canada so we don`t share the same selection of stores , my loss of course .

CONFIRMED : the NGK plug you want is : FR5-1 , #7252 . It will not reference for application , get them to look up the part #

[rightaway]

ok, i will look in my local store for those plugs. i think i might just do a full tune up. how does this look.
http://store.summitracing.com/partde...5&autoview=sku

i see that they have other kits from accel and moper. but i dont see a big difference for the price. i will also order a coil too. are the ngks one range colder? and what gap did you use?

[onegoodmason]

the NGK`s are a little colder plug , I`m not sure how much though . 40 thou was my gap , but only because I have the MSD coil , stock is 35 thou .

I`d just get the plugs for now , I bet they make all the difference in the world

[rightaway]

why would a spark plug make that big of a difference?

[onegoodmason]

why would a spark plug make that big of a difference?

Before trying the NGK plugs , I would have soooo recomended the dealer application , I use it religously on all vehicles I`ve owned and had great results , no missing , poor performance , etc . Just what I was experiencing on the jeep , no "problems" . Fuel comsumption is high on Jeeps , that`s a given , but my mileage was average low I`ll call it , so , I was thinking there was room for improvement . A good buddy on JU recomended those plugs last may when I did the engine , I didn`t listen . Again , the subject came up on JF , and again , another respected member reco`ed these plugs , so , figuring it was cheap enough , $25 Can . , I`d give it a shot .

Very first thing I noticed , and I think this is the answer to your Q , they were longer , noticably longer , I`ll guess 3/16" . When the spark itself can be delivered as close to the piston as possible , it`s a better bang . The spark is more centered in the chamber and therefore accually burns a higher percentage and the "explosion" is more centered and even , burning cleaner , some fuel always manages not to ignite or burn off during this process , these plugs help reduce that , therefore the better idling I`m claiming I could immediately hear, better power(but nothing major , just a little better I`ll say) and in the end , it takes less pedal to move the jeep resulting in better economy . As for being a cooler plug , maybe that helps somewhat too , but I personally think the length is key here . The 2001 engine I`m running had a longer set of champs in there (I didn`t use , I went dealer new), they gave me shorter ones , double checked the #`s , and off I went , not knowing better .

Right now , I can cruise at 50 MPH and get 17-22mpg , 60 is 15-18mpg , 70 is 14-18mpg and 80 , which is my cruising speed mostly , I`m 13-16 mpg`s . This IS using the overhead console , some say it`s inaccurate , but mine has always calculated out to be just a 'point' or 2 off , not enough to consider it innaccurate to me (all jeeps are different)
Don`t be fooled , I can bring those #`s down in a heartbeat with a touch of the gas , these #`s were based on using the cruise control , all of which were 3-4 mpg lower B4 the new NGK`s . Remember , this is lifted 5" on 32`s

After my speal , you`d think I own the NGK company or would benefit in some way from the purchase , but I don`t . They are a product that is working for me , I`ve noticed a big(3-4mpg) difference in economy and think you should try them out . If they weren`t , working for me or came highly reco`ed to me , I wouldn`t plat it forward . I`ve tried it all , air filters , K&N PFIK , MSD ignition and even replaced the Bosch O2 sensor back to a Mopar sensor , nothing made the change until adding the plugs and I`m back to the original air intake and filter system , but just for the winter

[rightaway]

you dont think with the longer spark plug will hit the piston?

[Goosed76]

it appears it's been done before without issue if they are saying they have installed them, and the thing ran- hence the claimed MPG increase...

[rightaway]

the only reason i ask if it would hit was on ngk list,
http://www.ngk.com/results_fitment.asp?pid=7252
it looks like it make for the 4.0 and later 5.2. i'm goin got try it out and see what happens

[rightaway]

this will be a couple of months recap on what had happen to me. i was towing my trailer and crank bearing went bad. after a long story just to get the trailer and the jeep home. we torn her down and saw that we need a new crank and bearing. we pulled the whole out, sent the block and heads to the machine. replaced all gaskets, and i mean all just. i have also upgrading the ignition systm and knn filter. and even after all this, i still only get 11 mpg