4.0 XJ questions regarding the engine

[Flyfishjeep]

I have a 20 year old Cherokee (1999) that I am the sole owner of. It has been a great vehicle but is now sitting at just over 250,000 miles. This has been a great vehicle and I have tried to take care of it. I have never had any major mechanical issues that I didn't cause (none to the engine anyway). It still passes smog (California no less LOL), but it seems tired. I am not super mechanical and know little about engines. My real question to all of you experts is simple. Should I replace the motor, or are them some things I can do that will "refresh" an old engine? I don't mind spending a few grand. I hear things like replace the timing chain, replace the jets in the fuel injection, and I am sure there are many more. I would love to hear from all of you willing to offer an opinion. I figure a new engine will set me back somewhere around 5-6 grand if I have a shop do it. Thoughts appreciated.

 

[danof76]

What have you done to the engine already? Any notable maintenance in recent years other than run of the mill stuff?

If you’re willing to invest a ton then start simple and clean the intake, throttle body, replace the O2 sensors, spark plugs, maybe even the cat.

The 4.0 is very robust, if it’s acting sluggish I would bet you could do one or more of my suggestions and yours without replacing or even rebuilding the current engine and get it back to feeling much better. There’s supposedly even one guy with 650,000 miles on his original engine; he is on his third tranny though!

 

[TylerA23]

I’ve got a ‘98 XJ.

Check out Cherokeeforum.com if ya haven’t. I have practically zero mechanical ability, but with that forum and YouTube, I’ve conquered everything thus far with my XJ.

Like mentioned above, I’d do a good tune up (plugs, wires, distributor cap/rotor), O2 sensors, change all the fluids with decent/quality stuff, filters, etc.

KSuspenion is VERY popular source for injector upgrades , other things (battery cables, headlight harness).

Good luck and I’m hoping to hear she’s back to her old self soon!

 

[NatersXJ6]

The engine at its core is probably just fine. The fuel system, cooling, etc are performance and failure points to be addressed and not included in your $5k new engine. If you buy a long block most places put all the old “stuff” back on the new engine.

Do a good compression and leak-down test then make some decisions. Odds are high the block and rotating assembly are fine if never overheated.

 

[ThePartyWagon]

I'm in a similar situation; 2000 XJ, 195K on the motor, body is in pretty decent shape but she seems tired out. Coincidentally, I cannot get the emissions monitors ready to be tested and I have a rough idle and/or misfire but no CEL. Someting is chirping on the top end of my motor too, quiets down after the engine gets to temp, thinking its my lifters. My future plans will be a new set of spark plugs, new exhaust from the down pipe back, including new O2 sensors. Fluids, injectors and if that doesn't solve much then I will throw in a new coil rail to see if that smooths my engine rumbles out. A quality battery can go a long way too. Pull the IAC (I think that's what its called) and clean it with carb cleaner, usually some gummy deposits in there.

 

[HercDriver]

Honestly if it runs fine then dont do anything until it breaks. Of course you could get new belt, timing chain, waterpump, t stat, headgasket and all the other gaskets and it would probably run fine.

You can also grab a shortblock from a reputable builder if youre worried about mileage. Quadratec has an engines for sale for about 2,700 bucks. You would just have to swap all your intake/exhaust manifolds and that stuff over to the new engine. Probably not a bad deal as you dont have to pay for labor to install all the parts like the timing chain and all the internals. See link...

ATK Engines Replacement 4.0L I-6 Engine for 00-01 Jeep Cherokee XJ

ATK engines with cylinder heads are engineered & fully remanufactured, using only the highest-quality parts and precision-machined tolerances.

www.quadratec.com

 

[wADVr]

Mentioned above is to get a compression and leak down test done. That will tell you where you’re at, at least for the cylinders and heads. Does it run quiet or have piston slap or knocks? I assume it doesn’t use or leak oil, how about oil in the air intake from the crank case ventilation system? I’d consider re fleshing some of those items and getting a compression test done.

The 4.0 is a pretty durable and long lasting engine, especially if you have maintained it well and haven’t beat on it too much, even with poor maint and beating they run a long time.

 

[borison]

^ yep

 

[SheepnJeep]

Could be a bit of a long shot but I would go straight to replacing the catalytic converter if it hasn't been yet. My wife's '93 Grand Cherokee 4.0 was getting slow and sluggish to the point that I thought the transmission was giving it up. Mechanic gave us the advice that the honeycomb baffle in cats can break down and pile up downstream in the pipe and block it. Ran totally "fine" otherwise. Replaced the catalytic converter myself easily and now she's back to her old self. Must have been bad a while we went from maybe 18 mpg highway to an easy 21 on average.