Yea, stretching is what they told me. I'm not sure which exact wire is causing the problem, and the dealership couldn't tell me. I think, because the problem is intermittent and not constant it's hard to tell exactly which wire it is. After connecting and reconnecting the plugs from the ECU, I had to zip tip the connectors to the ECU because the plastic clip that is supposed to lock them in no longer does. Thanks for the fuel injector wiring suggestion, Jerry.
Man that is really a crap diagnosis. I hope they didn't charge you for that. Seriously they plugged an ALDL in and looked for codes then didn't find any blamed the wiring harness and pushed it out. Really leaving you hanging and on your own. That in my opinion is really shitty work.
I may get it, if they told you that they will charge you real time for diagnosis and give you the option, but the way they left it seems like if you buy a new wiring harness, of which they didn't even tell you what you needed, and it doesn't fix the problem, that they are not on the hook. That is really BS.
I know me complaining about your dealership doesn't help your issue, but I don't think you need a whole new harness based on their diagnosis. Plus, I would be curious to how many patrons on this forum with lifted Jeeps have had problems with wire harnesses stretching. I am betting it is pretty rare.
Rather than spending money on a wire harness, (Unless you are going to get one for the dealer and they are going to put it in, and be on the hook for their diagnoses) I would spend a few hours at a reputable jeep shop for a better diagnoses. with the caveat that if it is a wiring issue, they fix it, or tell you what the issue is or you are not paying. Most shops wont actually deal like that, but what they will do is charge you two hours labor, and tell you where they are and then ask for more time, but if they haven't gotten anywhere they usually don't charge you.
Not being able to hear your Jeep or drive it I really can't help you much. I think
@Jerry Bransford is good advice, but if that isn't an issue, you are back at square one.
I don't know how much of a mechanic you are, but my advice would be to check for codes, but i am assuming you don't have any or the dealer would have been all over that.
Basically, if you don't have codes, I doubt you have a wiring harness issue, not to say it is impossible, but I think it is probably a more basic issue.
Here is my advice if this is something you can do yourself.
Pull your spark plugs. Look for them to be all of the same shape and color. If say they all are, and one is black, that will narrow down what your issue can be.
(In the same respect that the dealer said you have a bad wiring harness, you could actually have a bad ignition wire. Make sure they are all plugged in and tight. Make sure one is not just hanging there not snapped on.
Pull the distributor cap. I recently had a sputtering issue I couldn't find then one day on my way to work my Jeep just died. It had broken the end of the rotor finally. I missed it because it was intermittent. Although, that might be a moot point if yours is newer you don't have a distributor, but you will have a coil packs I believe, so I would check them for carbon tracks. although if you had a serious misfire, it should throw a code.
Next you should have a schrader valve on the fuel rail. If you have a fuel guage you can tap into that and see what your pressure is. If you have low intermittent pressure that could make it cut out intermittently. Also take a fuel sample like in a glass jar and look for water or gunk in the fuel. That is another possibility of issues that might not throw codes.
I know I am making a lot of assumptions, but a good mechanic will check the basics before telling you your Jeep is bad. At some point when cars get too old dealerships don't want to work on them and they will take your couple of hours of labor, and push you out the door. In cases like that, I think a specialty Jeep shop or even a 4x4 shop is even a better resource. I would actually advise an auto electric shop, but I don't believe in your diagnosis. I am really thinking you need a second opinion.
Sorry for my rant, but I am pretty passionate about good auto mechanics, and I don't think they gave you a square deal. I don't want to see you spend a lot of money have it not work then be back at square one. Spend a little more money and get a better diagnoses. They are just guessing, and I am betting their wrong. Especially because they have no liability in being wrong. If they are wrong, are they going to pay for your time and money on their bad guess? I don't think so. Don't buy anything unless you are sure it is going to fix it, and if it doesn't, make them take it off or eat the rest of the repair.
it is not your fault if they don't know how to diagnose something, so you shouldn't have to pay for them to practice, It is not like going to the doctors! It is not a practice.
Good Luck! again sorry for the rant, I hope I can save you some money, and get your Jeep back on the road at the same time.