Originally posted by Stocker
How about tires/wheels? Larger, heavier will have an effect on fuel mileage....
Maintenance? Old plugs & other ignition items are bad... A dirty air filter will hurt... O2 sensor maybe? Or a bad cat....
Another thought - does he have a manual trans, and you an auto? That would sure do it! (Note - was a manual available on a 4.0 98 ZJ?)
yea i see where this is goin...my brother and i have identical jeeps....the only difference that we know abotu it i have rear view mirros that defrost and he doesnt. he has a back window that opens and i dont. he can recirculate his heat and i can only do my cold.
same tire size, same tranny, im not sure about the t-case, but i think he has the 242, which is what i have. we both have k&n air filters, stock box drop-ins. i have bosch platinum 4's which i recently was told arent that great in the 4.0 engine, but i know thats not the reason because he has the same plugs as well.
so far these are some of the things ive come across that may be possible reasons for the difference
1. the 4.0 in 98 has more horsepower--not true. power did not change until 2000
2. final drive ratio. possible differnet gearing. not true. gearing did not change over the 2 years.
3. possible tps adjustment. not true. setting is alrealy at .74 volts
4. dirty air filter. not true. cleaned, charged, lubed, and put back. no difference.
5. possible fuel filter. not true. replaced and no difference.
so now im goin back to basics. air flow is fine. no problem noted there.
the only thing i can think of is maybe my cat is clogged. im sure its possible with 120, 000 miles. so i have to look into that this weekend.
could it be possible for the timing chain to skip a tooth, and my timing be off? i know there supposed to be done every 60,000 and im at 120,000 now so im lookin to get it done anyway.
im gonna try to check the compression of the cylinders as well.
im ordering a tbs, high flow cat, and cat back but i really dont wanna put it back on until i fix the problem, cause whats the point of doin it if its only gonna restore power that it should have anyway.
the way im ridin now im getting about 11 mpg city and 14 highway, and my window sticker says 15 city 20 highway, i know its not gonna be the same now, 7 years later but i mean at 11mpg i shoulda got the 5.2, or the 5.9 for that matter
i havent had any codes at all, so im not worried about 02 sensors yet, but i have taken it into consideration.
so besides the cat being clogged and me testing compresion and timing im all out of ideas