Home Forums Gear Hunting Trucks and Four-Wheel Drives Daughter's Jeep?

Those 4.0 straight 6 engines will run forever, so your's seems to be the exception to the norm.

My 1983 has a 4.0 in line injected 6, 5 speed

She doesn't have a 4.0L engine.

The engine in her Jeep is the older 4.2L or 258ci engine. The engine either sat too long without being used or the rebuild was bad. I could probably rebuild the motor, just lack the proper tools and more importantly time to do it in my garage.



Must be a 1993, unless someone did a swap? 1983 would make it a CJ Jeep. The 4.0L common rail Jeep motors didnt exist untill 1988 in the XJ Cherokee and 90 or 91 in the YJ Wrangler. Also anything after 92 would be the 4.0L H.O. motor.

I didn't realize that Jeep used a straight 6 other than the 4.0. I had a 1986 Cherokee with a 2.8 V-6 that was a bad motor. I got it from an USAF guy who was transferred while deployed to Iraq in 1990. He left the title with his buddy and I bought it for $500, a steal even with the crappy motor. I drove it for awhile and then sold it to a local girl as a school car for what I had in it.

Oil fouled plugs? Does your coolant look good?

I hope it's something simple and quickly made right.

If you buy new, an LS swap would be pretty cool. And not to much difference in money. But this would lead you down the rabbit hole of better transmission (AX15 would work with V8 but better choices out there), lift, tires, ect.

Its one of two things, valve seals, or the rings were installed wrong, the valve seals are a simple fix that you can do in a couple of hours, if that's not it, I would say the rings were installed with the gaps aligned or the wrong oil rings.

Can you still go back and talk to the person/company that rebuilt the motor?

Find a mechanic you can trust and he will know the best rebuild shop for the work.

i would replace the valve seals and see what happens then....if that doesnt fix it then proceed to a replacement

I didn't realize that Jeep used a straight 6 other than the 4.0. I had a 1986 Cherokee with a 2.8 V-6 that was a bad motor. I got it from an USAF guy who was transferred while deployed to Iraq in 1990. He left the title with his buddy and I bought it for $500, a steal even with the crappy motor. I drove it for awhile and then sold it to a local girl as a school car for what I had in it.

My Daughter bought a 88 Jeep Wrangler YJ for her first car with her own money a little over a year ago.






The 258 inline six is burning oil, we're to the point it's burning 5-6 quarts every oil change and we're doing a spark plug change every 3K miles as well. Engine has great compression in it 125-130 psi on all six cylinders. The engine is a rebuilt and I had sitting on a stand in my garage for a few years as a spare for my Jeep, that we swapped in after her original engine tested 50-60 psi on cylinders 5 and 6. Engine was properly broke in after install, but it has always used oil. This makes me think the rings were installed wrong or the valves never seated properly. She tried to get 6K miles out of the last set of plugs (L to R cylinders 6 to 1):




I converted it to PFI Systems TBI fuel injection shortly after she bought it, which made it a lot more reliable as far as starting and running. She wants to keep the Jeep which I understand as I have an 84 CJ7 that I love, and she has another vehicle to drive that's very reliable and she can take it with her when she graduates HS in the spring. She's 17 currently and a pretty good driver, but she's 17.

So I'm looking at options for the engine, and here is what I come up with.

1. Rebuild her 258 ci engine that's currently on my stand or order a rebuilt long block. $2500

2. Find a 4.0L core and drop a rebuilt/reman 4.0L running the current intake with TBI fuel injection. $3000

3. Find donor Jeep with a 4.0L and AX15 transmission, upgrading her to MPFI and a stronger transmission to eventually run bigger tires. I have a line on a running 99 XJ Cherokee with 150K on it but hit hard in the rear quarter for $1500 obo. I'm guessing $5-6K total if I decide to go through the engine and transmission before swapping with over runs on things.

4. Install a 4.3l V6 and AX15 transmission, this will set her up for a future LS motor swap and bigger tires. I just don't think shes ready for a 300 HP V8, that'll drop 100+/- lbs of weight total on the vehicle. So that's my reasoning for not going with a 5.3 or 4.8L motor right now.

...Find a Toyota tacoma.. Problem solved..

Whoever rebuilt that motor didn't know what he was doing. I would not put more money into it.

How about finding a deal on a low mileage stock motor?

I picked up a used complete 4.0L the other day out of a 93 Jeep Cherokee for $400 with all the engine accessories including MPFI . I need too do a little tear down and look it over, as it may just bee a core for a long block depending on what I find. I may just keep running the TBI injection I got or if I can source a complete engine wiring harness it might change over to MPFI.