(1998 4x4 I6 200k on engine, possible rebuild)

Okay as some of you may remember when I first got my Jeep almost two years ago(two years in may). I had a misfire on cylinder 1 & 2. Always both together never just one or the other. I have no coolant loss, and no oil loss. (for the most part- rear main leak) And I get about 18/20 mpg highway(doing 70 nothing faster, nothing slower and depending on the wind direction) , and between 12-16 city. Depending if Im wearing my heavy shoes or not. haha sometime you just gotta make that engine growl! Well fast forward to this past fall.. My check engine light wont come on unless I give it gas, let off, then give it gas again..like all of that real quick. Or something like that. If I drive like a grandma, it will actually just turn off on its own. I have a code reader at home. Now, its not saying I have a misfire on cylinder 2 just 1. Still no coolant in the oil or over heating or anything like that. Now I have not done a compression test or leak down, as Im going to assuming many of you are going to ask me to do. But I was just wondering what y'all thought it might be? And with 200K on the clock, would it be worth looking for a new engine to rebuild when/if I do a Comanche swap? Im just trying to plan everything out so I can do the whole swap in hopefully nothing longer than two months.

I hope I explained all of that coherently & thanks in advance,

-Zack

 

Could be many things. Possible causes, off the top of my head: plugs, wires, cap/rotor, injector(s), vacuum leak, loss of compression (various causes), carbon buildup on valve(s), valve spring(s).

 

I guess I should have stated all of that... I have changed the plugs, wires, cap/rotor multiple times, different brand etc to no effect. With the injectors I got 703s, and have moved them to make sure it wasnt one of them, I have checked for a vacuum leak I dont know how well, but I have. As far as the carbon, I have done sea foam, the mopar sea foam stuff, the old school water way and the fuel additives. All to no avail. And I would use theres no way to check the valves other than a tare down. And I would assume getting decent mpg on a lifted xj would mean my compression is okay, but I dont know why I would be 'misfiring on 2 and then just stop.

I also forgot to say that, this is the first truck Ive ever worked on. So two years ago I was a complete noob, and didnt know a lick of anything car/truck related. And when I got it, it was from an auto auction. So I dont know how this started or why. And it didnt really 'run' but when a clean tank of gas, a new fuel pump and plugs/wires/etc and idled rough but she ran.

 

In that case, I'd change your valve springs, at least on the affected cyl(s). Your engine is affected by the 96-99 TSB that addresses this.

 

Zack

Have you checked the cable between the engine and firewall? It was the source of my mystery misfire.

If it is the same issue as my 1997, then look VERY closely at the wiring harness between the engine and firewall.





In my case it was the sharp end of the fuel manifold. Others had one of the head bolts cut/ground the wires. Cheap fix.

I spent hundreds of $$$ chasing my tail on idiot codes and "professional" jeep mechanics.

 

You're right. Perform either compression test or a leakdown test.

Good data = good decisions.

Do it.

 

Whats that?

Ill check that tomorrow when its day light out if I remember




Well that'll have to wait till spring break I guess.. I dont have the tools to really do it here at college...I do, but id rather not.

 

The TSB applies to '96-99 4.0 engines. Basically, if you have a misfire and everything else checks out OK, you are supposed to run the Mopar Combustion Chamber Cleaner and then replace your valve springs. It cured a chronic #1 cyl misfire on my '98.

But yes, definitely check compression. If you have a compression gauge and a spark plug socket and ratchet, it wouldn't take long.

 

If my compression checks out and its not the wire thing Im basically 100% sure its the valve springs like youre saying.

Ah, yeah Ive ran the Mopar Combustion Chamber Cleaner though it before. No I dont have a gauge with me, but at home i do. And Ill be home first weekend in march, so I will post back then.

 

One thing, not sure how much difference it makes: the directions on the can of CCC say to let it soak for a short time, while the directions in the TSB say to let it soak a couple hours, then warm it up and do a few runs up to redline. However, since you've tried the CCC and also the water, I'm sure you've got it cleaned out.

 

Its not the wire issue mine doesnt come anywhere close to like what it does the pictures in above..thanks for the tip though I could see how that would be an issue.

I did the can, like this past spring and the water this past mid summer. I let it soak in for a short time, if I remember right like 3 minutes? Whatever was on the can. And like a 1/4 of it I think I did through the TB while it was running. Im going to guess that mean its the springs then.


Well since I guess if I'm going to have that all opened up I might as when do a rebuild. OH! I do have bunch on ticks, knocks, sounds, I dont have a good enough ear to hear the differences. But Im sure y'all could. I'll get a video tomorrow

 

For springs? All you have to do is pull the valve cover, find a way to hold the valve closed (either air or the old rope trick), and use a simple spring compressor.

 

Yeah but with 200k and ticks and knocks, shouldnt I just go ahead and do i all? Still working on that video btw..

 

I'm not an expert, but with 200K a rebuilt head would seem the minimum. Possibly a rebuilt engine or a good JY engine.

Be interesting what those more knowledgeable say.

 

Lets see if this works:



This is off of a cold start, where my jeep hasnt been driven in three weeks. You can hear the knock/tick it sounds to be coming from the back. And it goes away when its warmed up, and at higher RPMs