Post by: jeepster on March 13, 2016, 02:56:52 PM
I got a jeep 4.0l question for the jeep guys here.
First of all, I find the Internet very confusing these days, way too many other forums where immediately after somebody asks a question it just turns into a flame war, and can never find any real good info. I'd rather ask a question here on Hunt Wa and get an "I don't know" or a "not sure" than any other site.
Anyway my question.... I got a 2001 TJ with the 4.0 with 105000 miles and my mileage is in the pooper, I'm getting like 12.5 mpg, about 180-190 miles per 14 gallon tank running mid grade. It should be getting 15-18 mpg, but not. I obviously need new tires, and I've opened up the intake and exhaust, and I'm going to do the oil change (Mobil full synthetic + zinc additive) Tuesday but even with fresh oil, it might get to 13mpg, for a few weeks then drop back down. It's been idling periodically like crap too, takes a while to start, acceleration is ok, but, everything is kind of pointing to fuel injectors. My first thought was the valves, but to my surprise I found out it has hydraulic lifters and adjusters, which in some ways is convenient (being a mechanic, kind of disappointing for weekend jeep tinkering), but after some readin, it's really sounding like its fuel injectors.
My thoughts, and the way I work, is if something is going to get removed, upgrade it to something better than it was, so, i am considering doing the "Ford 4 hole" or Bosch injectors. The logic is that the injectors will give a better spray pattern, better atomization, thus better burn rate, and compared to tired old stock injectors, it should be a small performance increase ( getting my engine acting like-new). I realize the limitation of the jeeps ECM, o2 sensors, and understand that simply putting larger injectors into my engine won't change anything, because of the parameters in which the engine is designed to run, and that the brain and fuel pump will still only shoot a certain amount of fuel into each cylinder regardless of orifice size on the injector, but again, it's about the atomization and spray pattern, unlike a carbureted engine where you can swap out jets and monkey with timing and get more power when coupled with other minor mods. the numbers I'm getting for injectors are for the non "High-output" 4.0 are either 19lbs ford or 22lbs ford injectors, and for the "High-output", you can go up to 24lbs.
So what I am wondering is if anybody has done this (mod works on any 4.0l), or has even heard of this, and hopefully could give some insight.
Stock wheels, 30" tires, glass pack exhaust, super chips flashpaq tuner currently reset to stock, mileage hasn't changed on performance [rich fuel air mix] or econo [leaned out] and a custom cold air intake (more like hole saw and sawzall job to the stock box, and replacing all the correggated intake pipe sections with hose)
I am also thinking about increasing the plenum between the manifold and throttle body by adding a spacer.....
Anybody have any other mileage increase ideas aside from doing an engine swap for a turbo diesel 4 banger?
Post by: jackelope on March 13, 2016, 04:45:24 PM
Post by: deerhunter_98520 on March 13, 2016, 04:51:37 PM
Post by: papisjeep on March 13, 2016, 05:38:29 PM
even worse if it had auto trans
Post by: jrebel on March 13, 2016, 07:17:13 PM
Post by: Alchase on March 13, 2016, 07:18:14 PM
I would break it down to basics. Plugs, wires, fuel, proper tire inflation, either can make a couple mpg difference.
A word of advice, unless you have ran synthetic oil the whole time, I would not recommend starting synthetic with over 100 k miles on a 4.0. Everyone I knew the tried synthetic on high mileage 4.0s ended up with rear main leaks.
The 4.0 is a strong, long life motor if kept with clean oil and basic maintenance, it has never been called a gas miser, and honestly no tuner or after market gimic has ever made the 4.0 anymore efficient. Believe me thousands a thousands of jeepers has thrown the kitchen sink at it.
Post by: jackelope on March 13, 2016, 07:58:40 PM
Post by: huntandjeep on March 14, 2016, 06:51:05 AM
Post by: deerhunter_98520 on March 14, 2016, 08:35:12 AM
Post by: Special T on March 14, 2016, 08:44:22 AM
I saw a pretty ridiculous price on reman4 hole for about $12 ea plus shipping. Ill probably go new. my injectors have 200K plus on them
Post by: Wazukie on March 14, 2016, 09:15:20 AM
Post by: Cougartail on March 14, 2016, 09:53:02 AM
Post by: Alchase on March 14, 2016, 10:00:40 AM
Rear mains leak on 4.0L's running synthetics or not. I've probably literally made mortgage payments off the commissions I've made selling 4.0 rear main seals.
This is a true statement!
But, mine did not leak until 185k on one and 206k on the other using dino oil. And almost all of our XJ group who switched at high miles, leaked within a short time. Way too many for it to be coincidence.
Post by: jackelope on March 14, 2016, 10:07:44 AM
Rear mains leak on 4.0L's running synthetics or not. I've probably literally made mortgage payments off the commissions I've made selling 4.0 rear main seals.
This is a true statement!
But, mine did not leak until 185k on one and 206k on the other using dino oil. And almost all of our XJ group who switched at high miles, leaked within a short time. Way too many for it to be coincidence.
What' a MJ?
Post by: Alchase on March 14, 2016, 10:33:28 AM
Oh My they get no respect! LOL
The MJ is the Comanche pickup, an XJ with a bed, LOL :hello:
Post by: jeepster on March 14, 2016, 10:34:12 AM
Rear mains leak on 4.0L's running synthetics or not. I've probably literally made mortgage payments off the commissions I've made selling 4.0 rear main seals.
This is a true statement!
But, mine did not leak until 185k on one and 206k on the other using dino oil. And almost all of our XJ group who switched at high miles, leaked within a short time. Way too many for it to be coincidence.
What' a MJ?
A Jeep MJ is mommy's Jeep :tup: :chuckle:
Kidding aside, its the Comanche, the Cherokee based pickup
Yeah my tj leaks and has leaked for a while, I've ran synthetic whenever I could afford it for the last 5 years, and regularly for the last 2. Bought this thing used in 07 with 14,000 miles and plan on having it alot longer.
Guess I've been working on diesels too much... If they run like crap, change the oil, do the valves, drop in new injectors, give it new filters and call it done
So if you say put on a new cat and 02 sensors, couldn't I bash the kitty and install dummies? It's not like I'd ever have to get it emmision checked, I live on North Whidbey and plan on going to Alaska, so, I'd never smog it.... Not exactly legal but.... It don't bother me. Probably would be cheaper... And would never have to worry about it again.....thoughts?
Post by: Alchase on March 14, 2016, 10:37:25 AM
Rear mains leak on 4.0L's running synthetics or not. I've probably literally made mortgage payments off the commissions I've made selling 4.0 rear main seals.
This is a true statement!
But, mine did not leak until 185k on one and 206k on the other using dino oil. And almost all of our XJ group who switched at high miles, leaked within a short time. Way too many for it to be coincidence.
What' a MJ?
A Jeep MJ is mommy's Jeep :tup: :chuckle:
Kidding aside, its the Comanche, the Cherokee based pickup
the Wish-I-was-a scramber pickup :chuckle:
Post by: jackelope on March 14, 2016, 10:41:17 AM
:yike:
Oh My they get no respect! LOL
The MJ is the Comanche pickup, an XJ with a bed, LOL :hello:
Gotcha. We never saw too many of them at the dealership. I can remember 1 guy who spent a God awful amount of money on one, but that's the only one I can reliably remember.
Post by: HUNTINCOUPLE on March 14, 2016, 11:55:22 AM
Post by: Thehowler on March 14, 2016, 12:48:48 PM
Before I did all my own wrenching, I had a jeep wrangler in for a running issue at 99,000 miles. One thing they called back that needed to be done urgently, was my very dirty fuel injectors needed cleaning, and also a new Map sensor. I had them only do the map sensor and it ran light a top. I never once cleaned those fuel injectors and ran that motor for 275,000 miles before rebuild. Always Chevron gas.
Post by: jackelope on March 14, 2016, 03:56:25 PM
Post by: rudysts on March 14, 2016, 04:20:31 PM
Post by: Thehowler on March 14, 2016, 05:28:14 PM
Have you heard of a injector- fuel system cleaner called BG44K, PN 208? I've talked with a few folks recently that swear by dumping a can of this in a full tank of gas.
Post by: jackelope on March 14, 2016, 05:44:58 PM
Post by: Wacenturion on March 14, 2016, 06:23:11 PM
Post by: dewandgin on March 14, 2016, 08:48:00 PM
Jackelop,
Have you heard of a injector- fuel system cleaner called BG44K, PN 208? I've talked with a few folks recently that swear by dumping a can of this in a full tank of gas.
Used BG44K all the time when we used BG. I have friends that use it to smog vehicles in California. Vehicle will not pass running to dirty. Put a can of 44k in the tank fill it up and go drive it for 30 miles and smog it. It will pass almost everytime.
We have 2 CDJR dealerships and I have rarely/never seen a 4.0L with a automatic 4X4 get more than 15mpg on a really really good day. Check for exhaust leaks at the exhaust manifold cracking and make sure you use champion plugs (in my experience the run better and smoother) and as others have said tires aired up, tuned up and smooth starts and stop.
My 4.0L Cherokee has never got more than 14mpg.
Post by: Alchase on March 15, 2016, 01:37:55 PM
I had a 2001 Cherokee that had an idle issue it had nothing to do with the injectors. it was much worse it turned out to be a cracked head this is actually a common problem for 99-01 years. I hope you don't have that problem good luck to you. you can easily google this problem.
A cracked head on a low miles 4.0?
That one is new to me. Even the ones that had the cooling system issues and overheated rarely ended with a cracked head.
The MAP or MAT sensors, EGR, TPS can cause a loss of power or MPG as well.
Post by: jackelope on March 15, 2016, 02:57:13 PM
The exhaust manifolds break all the time. Down near the collector.
Post by: Thehowler on March 15, 2016, 05:15:12 PM
Post by: coachcw on March 16, 2016, 06:39:21 AM