Jeep sputters while accelerating

If it's sputtering there should be a check engine light. If there isn't yet, there will be soon I assure you (so keep driving it until it comes on).

Unfortunately it's very hard to diagnose issues like this with no CEL or error code.
 
Good idea. Otherwise it's pretty much like firing shots in the dark. We can guess, but there's no real accurate way to know.
 
Code 43 is the only real code you have there, 12 and 55 are nothing to worry about. 12 means the batteryhas been disconnected at some point, and 55 means the end of the self diagnostic mode.

Code 43 means misfire. The issue is that that is pretty vague still. I believe if you hook it up to an OBDII scanner (any auto part store will do this for you for free), it will at least isolate the cylinder that is misfiring. I could be wrong about that, but I don't think so.
 
BTW, this was taken from an old post by @Jerry Bransford that is related to your issue:

There is an official Jeep TSB (technical service bulletin) specifically for this problem, though there's no guarantee of a complete fix if you perform the TSB. Some early 4.0L engines in '97 and early '98 came with a bad (weak) set of valve springs from a bad batch which is what causes the misfire for a good percentage of those getting the 43 DTC. The TSB instructs that the valve springs be replaced and the engine be de-carbonized afterwards.

My '97 often even had multiple 43 codes at once (like 12 43 43 43 55) and before Jeep came up with the TSB, I fought the problem for years to the point that Jeep engineering actually contacted me after reading of my pleas for help on the various Jeep forums. The engineer who called me (none other than THE Jim Repp, "father" of the Jeep Rubicon) sent me a care package of components to swap into the Jeep one-by-one but none of them helped. The kit had all new fuel injectors, fuel injector wiring harness, PCM (engine computer), clockspring, and a few other odds & ends. I had already replaced everything in the ignition system including the plugs, ignition wiring, distributor cap, and rotor.

Then later, the TSB was issued and I replaced the springs which cut my repeated 43 codes by probably 80%. I suspect I had the 43 code occurring for so many years that the valves or valve seats might have burned a bit which is why I still get a very occasional 43 code code but it's rare compared to how it was before I replaced the valve springs. A friend had the same issue and a complete valve job with new valve springs completely cured his TJ and he hasn't had a 43 code in probably five years now.

Note that a TSB is not the same as a Recall so you will have to pay for any work performed under a TSB. Good luck with it.
 
Tristan said:
Damn, I hope that's not the issue. Don't really want to get that down and deep in it.
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Replacing the valve springs is an easy and inexpensive of a good first step, that's not a major job. BUT... it's been happening long enough by now that I'd seriously consider having a valve job instead which will (should) include new valve springs. At the least I'd have the new valve springs installed which can be done without removing the head from the engine.

And with your muliple 43 codes as my '97 TJ had, I'd bet serious $$$ those weak valve springs common in '97-98 are indeed causing your problem.
 
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Alright I'll look into getting some valve springs. Not too much work since I got to replace my valve cover gasket. It's got a pretty bad leak on the front.
 
Fortunately the TJ is a under-head cam design. That makes changing the valve springs soooooo much easier as oppose to a overhead cam.
 
Chris said:
BTW @Jerry Bransford, I'm surprised that Jeep engineering actually contacted you. I guess they secretly must be lurking on the forums.
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They did because the 43 code misfire problem was a very hot topic on the various forums & I was one of the first to ask multiple times for help on it. Jim Repp & I spoke often for the next couple years, he would also occasionally leak info to me on the Rubicon to post before it was finally released to keep the rumor mills under control. :)
 
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How difficult of a job is it to change the springs? I'm no mechanic but I know enough to get in trouble and love learning. I'll be going to a shop that will have pretty much any tool known to man.
 
Tristan said:
How difficult of a job is it to change the springs? I'm no mechanic but I know enough to get in trouble and love learning. I'll be going to a shop that will have pretty much any tool known to man.
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It's not difficult and no valve adjustments are needed afterward. But you have to insure the valves don't drop down into the combustion chambers as you unfasten the rockers. If the piston for that valve is at the bottom of its stroke, the valve will fall down inside the combustion chamber if you don't prevent it from happening. :eek:

That can be prevented by either feeding a small diameter rope into the combustion chamber viat the spark plug hole to stuff it full of rope, or by pressurizing the combustion chamber with compressed air via a special hose adapter from a compressor that is threaded into the spark plug hole so the valves are held up against their seats. That last method's a little trickier since you have to rotate the engine to the right position for the valves to be closed during their compression stroke.
 
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Yep, everything Jerry said is spot on. It's pretty easy to do the valve springs on these engines. Like I said before, if you had overhead cams it would make it much more difficult.
 
Stockli said:
wait that was used for something different. Lol
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What? Clothes pins? Really! Of all the guides I read years ago on replacing the springs, none ever mentioned that method. That sounds like the best method of all though it'd be just my luck to bump one of them and that valve fell in. That is a cool sounding method though, I like it!!

New clothes pins with a real strong spring lol.
 
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