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My '96 XJ Maintenance and MPG thread

You should never, ever re-torque head bolts on a jeep 4.0
They are torque to yield bolds.


CorneliusRox said:
My 95 xj typically gets between 18-21mpg, and the best I've done is 26mpg on one trip (hand calculated) where we were driving about 55-60 the whole tank non-stop in summer.

I switched from crappy tires (brand was Winner) to Goodyear Wranglers (OEM size) and mileage went down almost two mpg! These tires are noticeably heavier (when rotating and they slowed down my low speed acceleration).

Spark plugs: I swapped to some iridium plugs and gapped them accordingly, then a month later tossed a MSD ignition in it. They both helped with mpg and idle. I recommend them. I even put them on my 95 YJ as well.

Injectors: I have bought new OEM injectors when I bought this Jeep, then two months later swapped to the Neon ones, and I picked up about .5-1mpg and gained a super smooth idle. It didn't feel any faster.

Trans cooler: I used a Ford 6.0L diesel trans cooler, Earl's AN fittings, and Aeroquip hose from the trans to the front. I haven't had a leak or issue ever. I'd also recommend an in-line filter header for the trans fluid (so you can change it like a oil filter for an engine). I typically do this on my vehicles (even though I haven't done it on this one yet) and it keeps the trans fluid Super clean. Way better than the little pickup filter.

If you're taking the header off, port match the head and header. Lay the gasket over the head, spray it with something to mark the location, and grind away. Your EGTs will drip slightly and your peak power will go up ever so slightly.

I'd also take apart the throttle body and clean it while you're there. The idle control likes to get cakes with blowby gasses.

Oh, and the last thing, retorque your head bolts.
Click to expand...
 
Johnnie Walker said:
Engine does not need to be running. Should work KOEO or KOER
Click to expand...

I wonder if that varies between vehicle manufactures. I had some trouble so many times with mine, I forget when it does work right, LOL. I kept forgetting to turn the cell phone bluetooth on.
 
Ecomike said:
You should never, ever re-torque head bolts on a jeep 4.0
They are torque to yield bolds.
Click to expand...

Putting on my engineering hat, I'd 100% agree with you.
Putting on my performance vehicle hat, I disagree.

A lot of people will overtorque the stock head bolts ~10ftlbs when throwing boost at it. Keep in mind, you're looking for the upper end of that bell curve. By that, I mean that most people will grab two sets of head bolts and just replace the bolts that are overly stretching.
I personally have done it where I backed them off, lubed, and got a good dynamic torque with a digital torque wrench, one at a time. Currently I'm using ARP head studs because they're cheap and have WAY better clamping loads than head bolts.


NOTE: If you go the stud route, I recommend bottom tapping the bolt holes in the block. Also, you can do one at a time and save the head gasket (but might as well replace lifters and head gasket while you're in that area.)
https://www.summitracing.com/parts/arp-146-4201/overview/
 
Last edited:
Ecomike said:
Used these (link below), new on my 89 ten years ago, followed the OEM FSM spec for installation and never looked back, over 100,000 miles added since then with zero issues.

http://headbolts.com/jeep-258-242-arp-146-3601-head-bolts

They were $15 cheaper then.
Click to expand...

Nice, I didn't know they made head bolts too. I wonder what the UTS of these vs the studs are. Either way, you can't beat the price on those. I'd go that route if I wasn't ever planning on adding some boost!
 
CorneliusRox said:
Nice, I didn't know they made head bolts too. I wonder what the UTS of these vs the studs are. Either way, you can't beat the price on those. I'd go that route if I wasn't ever planning on adding some boost!
Click to expand...

Its the same ARP brand bolts you suggested, just another dealer-distributor with better pricing.
 
Ecomike said:
Its the same ARP brand bolts you suggested, just another dealer-distributor with better pricing.
Click to expand...

Not exactly. I suggested studs. Those are bolts. Studs have more accurate torque (less twisting of the shaft section), and are typically higher UTS. Both would likely be a big improvement on the stock head bolts though! :cheers:
 
Last edited:
Got the cooler and air shocks installed.

Tranny fluid doesn't look great so going to change it. Do I need to drop the pan to change all the fluid or will it all drain out from the plug?
 
96Sportxj said:
Got the cooler and air shocks installed.

Tranny fluid doesn't look great so going to change it. Do I need to drop the pan to change all the fluid or will it all drain out from the plug?
Click to expand...

I forget if they even have a drain plug? Dropping the pan lets you remove and solvent clean the metal filter screen, and reuse it, and allows you to clean and inspect junk in the pan bottom. IIRC I was able to suck about 3 quarts out with a sucker hose tool out of the dip stick assy and drain as much fluid as pan removal drains, not more than 3 quarts at best.

These days I disconnect the Transmission fluid cooling line to the radiator and turn the engine on to let the Trans Pump, pump the fluid out into a drain pan(s). I forget if it pumps in Park or only Neutral. You drain most of the fluid that way, holds about 10 quarts I think.

If the fluid is old and dirty, I would drop the pan and use the 3 or so quart method method first. Doing a full 10 quart swap with old dirty fluid in it, and not dropping the pan can cause problems. Better to use 3 quart transfusions the first 1 or 2 times.
 
Ecomike said:
I forget if they even have a drain plug? Dropping the pan lets you remove and solvent clean the metal filter screen, and reuse it, and allows you to clean and inspect junk in the pan bottom. IIRC I was able to suck about 3 quarts out with a sucker hose tool out of the dip stick assy and drain as much fluid as pan removal drains, not more than 3 quarts at best.

These days I disconnect the Transmission fluid cooling line to the radiator and turn the engine on to let the Trans Pump, pump the fluid out into a drain pan(s). I forget if it pumps in Park or only Neutral. You drain most of the fluid that way, holds about 10 quarts I think.

If the fluid is old and dirty, I would drop the pan and use the 3 or so quart method method first. Doing a full 10 quart swap with old dirty fluid in it, and not dropping the pan can cause problems. Better to use 3 quart transfusions the first 1 or 2 times.
Click to expand...

Thank you for the tip! It has a drain plug so I am going to try the 3 quart transfusion method. Any recommendations on how many miles to drive before each change?

Also today is the hottest day we have had (75) and my temps show cooler. Would the upgraded tranny cooler (kept stock cooler too) be enough to show a difference on the temp gauge?
 
96Sportxj said:
Thank you for the tip! It has a drain plug so I am going to try the 3 quart transfusion method. Any recommendations on how many miles to drive before each change?

Depends on how dirty and burnt if any, the old fluid is, 50 miles to 12 months/10,000 miles. Its a judgement call. Does it look pint and smell like like new Dex III fluid, or brown and smell burned?

Only Use Dex (Dexron) III or Dex III-Mercon V fluid only, do not use anything that even mentions synthetic, or DEX IV,V or VI.

Also today is the hottest day we have had (75) and my temps show cooler. Would the upgraded tranny cooler (kept stock cooler too) be enough to show a difference on the temp gauge?
Click to expand...

NO.
 
Ecomike said:
NO.
Click to expand...

Thank you again! You can fill the outside of a barn with what I don't know.

Fluid was brown and burnt smelling. Have a 40mile drive tomorrow so I am going to do another 3 quarts after that drive.

Have an 900 mile round trip coming up towing 1200ish pounds so trying to get my ducks in a row. Also installed a new coolant temp sensor today.
 
In that case, add a pint or 1/2 pint of Trans-X with the fluid changes, and get the fluid hot and check the fluid level on a level driveway before topping it off with Dex III, to the full when Hot line. The level on the dip stick rises fast cold to hot and the last 1/4 Pint makes a big move on the dip stick so add slowly and be patient. The Trans-X will help slowly clean any varnish build up in the valve body parts and keep it shifting smoothly, it also rejuvenates old seals to keep them leaking. The Trans-X is also a good pre drain cleaner. Add it (say a 1/2 pint), drive 50 miles, then drain the 3 quarts, and add a 1/2 pint again) and the Dex III and drive the beast!!!
 
Ecomike said:
In that case, add a pint or 1/2 pint of Trans-X with the fluid changes,
Click to expand...

I read your thread on the trans-x, but I dont think I need it. She shifts smooth and other then burning some oil climbing a steep hill while towing I haven't had any issues. I drained and added another 3 quarts after a 70mile drive. The stuff that came out had more red then brown so hopefully the 6qrt fluid change is enough for now. I will continue to do the 3qrt changes with every oil change from here on out.

On a side note I had my buddy clear the codes with his code scanner and the jeep seems to be running smoother/quieter. So fingers crossed my MPG's come back! =)
 
Did another 100 mile trip and with 70/20 hwy/city driving while pulling 800-1200 pounds I averaged 16.3 mpg. So getting a little better. It has also been 75F+ this week. Really hoping to see 17mpg on my 1000 mile trip.
 
Just towed around 3kish pounds 405 miles and averaged just over 16mpg cruising around 60-70mph down shifted to third for the big climbs and she did great.
I have some pictures but no idea how to upload them. Where is the manage attachments option?
 
96Sportxj said:
Just towed around 3kish pounds 405 miles and averaged just over 16mpg cruising around 60-70mph down shifted to third for the big climbs and she did great.
I have some pictures but no idea how to upload them. Where is the manage attachments option?
Click to expand...

It is in the User CP page left side Manage Photos.... but I think you need to be a paid member to upload photos.
 
A year ago I would have never thought the ol girl would have made this trip.(820 miles) Now after reading through this forum and seeing what the old XJ is capable of with a little love. It will most likely be a twice a year trip for her.

Towing with cargo and passengers I am guesstimating around 2000 pounds.
Best hand calculated MPG was on I5 with the cruise set between 70-75 and she got 17.38mpg. Including going up one pass at 45mph in second gear. Same pass the XJ only got up to 210-215 degrees.

Was also impressed that with the tires down to 25psi she was one of the few vehicles that did not get stuck in the soft sand.

2 jetskis and a 3 wheeler on the trailer plus as much crap as we could fit.

0WjFxys.jpg



yoB4Mrc.jpg
 
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