I have a 97 TJ 4.0/manual thats been great on road and off - the only consistent problem I have with the Jeep is the MPGs, way less than advertised, I'm averaging 12-14 in city and about 16 on freeway.
I've checked everything out possible, and even taken it to the stealer; either I have a very heavy foot or I just have a thirsty jeep.
I'm basically annoyed by the gas mileage, so my question is- can I swap in an engine (or engine/tranny combo) that will give me at least the same performance (torque, power) and also has mpg in the 19-24 mpg range?
Sure its a lot to ask, but if its possible I'd like to do it and figure it would be a fun project.
So how many years do you figure it'd take to pay for the cost of the engine conversion with better fuel economy. My best suggestion is that you sell the Jeep and buy a Geo.
That is normal but if you put 13" tires on it, install a 2.0L engine, change the body style to be more aerodynamic, put a lowering kit in it, well heck you may as well go and buy a GEO.
Really? No wonder my kid bitchs about his TJ's mileage. My YJ(4cyl-5sp)gets better than 22, my wife's YJ(6cyl-5sp)gets a little better than that. Guess newer isn't always better...you're right after all, Bill.
-- Old Crow '82 Shovelhead FLT 92" 'Pearl' '95 Jeep YJ Rio Grande ASE Certified Master Auto Tech + L1 TOMKAT, BS#133, SENS, MAMBM, DOF#51
You would be better off to buy a Jeep with a 4 Banger already in it.
However, your problem may not be the engine size. Tire size, tire pressure, body lifts, axle ratios, and as you say, driving habits all affect mileage - usually much more than the difference between a 4 & 6 cyl. For instance, just try dropping your freeway speed by 5mph for a week and you'll likely notice a 2 mpg. increase. My 93 YJ with a 4cyl/5speed (stock tire size & gears, no lift) gets about 22 mpg if I drive at 55 on normal roads. When I get to the interstate, I typically drive 65-70 and my mileage drops to ~18 mpg - nearly a 20% difference in economy. The faster you try to drive a car with the aerodynamics of a house, big tires, and geared for offroad use, your fuel economy will suffer much more dramatically than if you are driving a Lexus. It is a lot cheaper to make some tire changes and driving changes than an engine swap.
Dana Rohleder Port Kent, NY
"Our enemies are innovative and resourceful, and so are we. They never stop thinking about new ways to harm our country and our people, and neither do we." G.W. Bush - Washington, D.C., Aug. 5, 2004
Well since no one else will jump on this one, I will, how much do you want for your engine? Would replace my old 258 in my CJ nicely, already have the AX15 tranny in it so would be a bolt in swap for me. You can get a chevy 350 turn key engine with 380 HP for $3500.00, wouldn't do much for your gas milage but would give your TJ a nice kick, then sell me your 4.0 L for say a grand :)
In my experience the aerodynamics are the mileage factor.
No matter the engine or the load they all get about the same mileage. It depends on your foot and the speed you want to run and/or the 'RPM'.
If I am running at a GPS checked 'real' 65 mph in 5th gear, my 33" tires keep my rpm down to about 1600 or so. It then sucks gas big time and I get down near 15 or 16 mpg. If I drop down to 4th gear at 65 mph and keep my rpm in the/my engine's 'sweet spot' of 2300 rpm, I get a consistent 23 mpg or 11 L/100km. I checked this a couple weeks ago running fully loaded for camping.
Then come gas differences!!!
If I run on 'real' gasoline, my mileage always stays up way over 20 mpg. If I run on any kind of alcohol or ethanol mix like my owners manual warns 'not' to do unless in an emergency because you are out of gas, my mileage is almost cut in half. The manual says the mix may 'degrade performance' before rotting out the fuel system. LOL! Yup, it 'sure' does degrade performance.
Have you checked your speedometer/odometer for accuracy?
Mine went 100% right on my CJ7 when I put 33's on it and it went 100% right on my Cherokee when I put 235's on it. That make a difference in the perceived vs real mpg....
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
What you would spend on doing this would be much much much much much more than what you would save on fuel. As Hesco says, "Speed costs money, how fast do you want to go?"
Your 4.0 should be getting better than that. Let's start off with the basics.
Plugs, Wires, Rotor, Cap
Clean the IAP
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If the plugs show rich (excess carbon) then you should replace the O2 sensor. Yes, it can set a code but the O2 sensor will drift off long before any codes get set.
Depending on how long you have ran the cat might need replacement.
You should also check your exhaust header for cracks. The 4.0 header is notorious for this. You know it's cracked when the engine sounds like a diesel or you start getting what sounds like lifter noise.
Switch out to full synthetic if you haven't already, that's good for a teeny improvement.
But by and far the best way to reduce fuel use is to take it slow and easy. The goal on the highway is to not have to use the brakes. And try not to beat folks to a red light. :) I tried driving like that for a couple of tanks and it made a 4mpg difference in my city driving. (then again my ZJ can gulp fuel)
12-14 around town and 16 on the freeway is NORMAL for a Wrangler. It's neither low nor high. My own Wrangler, built, gets right around 12.5 to 13 mpg all-around driving with obviously a bit more on the highway if I keep my speed down. The big issue is the Wrangler's barn door aerodynamics which don't help with fuel economy. Even the Grand Cherokee with the same engine will get better fuel economy due to it's vastly better aerodynamics.
The bottom line is that it's a Jeep Wrangler that is built for offroading, it's not an econo-box or car that has more going for it so far as having more potential for better economy. Once again... if you can't live with that fuel economy, it's time to get something else to drive.... Jeeps aren't for you.
Even with the aerodynamics of a brick, 4-5 mpg seems a lot of difference between the Wrangler and the ZJ. What kind of rpm does the Wrangler need to turn to cruise at 70 mph? The ZJ is loafing along at 2000 at highway cruise range and gets 20-21 at that speed.
Dunno how much improvement the OP would get by boosting the compression ratio a tad. Would bet not enough to pay for the modifications, but not everyone's priorities are the same.
I agree with Jerry. I have a built TJ (35" tires) and I get the same as he mentioned. I am between 2000 and 2800 RPMs' on the highway to keep the engine in it's sweet spot. I run 488 gears. The slower I go on the highway relates to better mileage. I'm planning a trip cross country and I've factored in the fact that I will have to leave a day earlier. Go slower.
Of course I don't mean to address the posters who replied in a friendly kind of way, but the majority of you stuck up elitists chose to make hay out of my being better served by a different car.
I asked if it was possible to drop in a more efficent powertrain on a Jeep because I'm annoyed by low teens in the MPG. If thats whats Jeeps get, well congratulations to all of you for being satisfied with an inefficient auto in 2004- in my opinion the extremely low MPG on the TJ is hilariously low for a modern vehicle.
If its an aerodynamics issue than there 4 banger shouldn't get better MPG - period. SO it stands to reason that the aged 6 cylinder in the Jeep is the reason.
Of course it is always amusing to watch the self-proclaimed experts on the Jeep board strut around as if anyone who doesn't share their WEALTH of knowledge and insight, and in this case, acceptance of a crappy aspect of a jeep is better suited in a different auto - I'll keep the TJ, thanks - and your opinions of whether I'm "suited" for it or not can keep your collective heads company up your bums.
Read it again and see if it doesn't shout, TROLL! "I have a 97 TJ 4.0/manual thats been great on road and off - the only consistent problem I have with the Jeep is the MPGs, way less than advertised, I'm averaging 12-14 in city and about 16 on freeway.
I've checked everything out possible, and even taken it to the stealer; either I have a very heavy foot or I just have a thirsty jeep.
I'm basically annoyed by the gas mileage, so my question is- can I swap in an engine (or engine/tranny combo) that will give me at least the same performance (torque, power) and also has mpg in the 19-24 mpg range?
Sure its a lot to ask, but if its possible I'd like to do it and figure it would be a fun project.
thanks." God Bless America, ßill O|||||||O mailto: snipped-for-privacy@aol.com
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