cmsaw83

I own a 1997 Jeep Grand Cherokee Limited 4.0L 2wd w/ automatic transmission. My Jeep is 100% stock, aside from the audio receiver and speakers I replaced all the way around, due to the fact that the existing Infinity stuff had all s*** the bed, except the amp. So I replaced the speakers, and the receiver, and installed a small, bridged, Memphis audio 250w RMS amplifier and a 12" subwoofer in a ported enclosure, which I fastened to the floor of the Jeep in order to keep it stationary. Like I said, aside from these audio upgrades, my Jeep is 100% stock. When I purchased it, I was just looking for the most affordable, yet safe, - for the most part - and reliable vehicle I could find to get me back and forth to work every day. I have owned 3 Jeeps prior to this one. Another Grand Cherokee (a 95' Laredo 4.0), and two Cherokees (a 94' "Country"/"Limited" 4-door 4wd model, and a 97' "Sport" 4-door 4wd model). Each of the Jeeps I had owned in the past were fantastic vehicles in every way imaginable, save one, which is gas mileage. But that is something that one just accepts upon purchasing a vehicle with the tried and true 4.0L engine. You may not ever save yourself a ton on gas, but until pigs begin to fly, you'll get where ever you are headed, and back home, without any hiccups... Typically

This 1997 model GC was njo exception, and got me back and forth to work for just over a year, before the ECM/PCM finally kicked the bucket, and she left me sitting in the bottom of the M&M tunnel, waiting for VDOT to come and tow me out of there, and drop me at their designated drop-off spot for broken down vehicles. After she broke down that day, she sat for a period of time that lasted about 6 to 8 months. I had an old 99 Taurus for a while, and I drove it to and from work for a while. Then the head gasket went on that, so it was time to get the Jeep running again. I wasn't immediately certain that the ECM/PCM was what was the cause of my break down earlier in the year, so before dropping $405 on a remanufactured ECM/PCM, I installed a new CPS, and a new fuel pump. When those didn't get her started and running again, I knew it was time to pick up a new ECM/PCM and give that a try. So I went to O'reillys, because they not only sell A-1 Cardone remanufactured ECM/PCMs, but they are one of, if not the only store in my locality, that actually keep them in stock.

I've heard too many horror stories about these components failing, and then people trying to save a few bucks, and purchasing a replacement off of EBAY, or some place similar, from some unheard of company who claims to "remanufacture" their ECM/PCMs, only to get it installed, and find that the one they just purchased, is no better than the one they took out of their Jeep that was bad at the start. Of course, after replacing the part, everyone assumes that the part they purchase is good, so when the vehicle continues to exhibit the same symptoms following the installation of the "new" part, they then begin the process of combing through EVERYTHING else, and wasting a ton of time, before they finally come to the realization that the remanufactured ECM/PCM they purchased was never any good, and then they are either past their return/warranty period, or they never had the option to return the part to start with, and so they end up having to just go and purchase one of the more pricey options anyway, in the end... So, this was my reasoning for going the route I did. Only, after installing the remanufactured ECM/PCM in my Jeep, and then wasting a TON of time combing through every single last part I can think of - including tracing each and every single wire to/from my ECM/PCM and other components, as well as removing each one from it's respective terminal, in order to ensure those connections were up to snuff, before replacing it, one by one, until I knew my terminal connections were all good - as well as purchasing the tools and materials necessary to re-do all of my ground wires, as well as all my positive battery terminal wires too (to starter, to alternator, to power distribution center/fuse and relay box, etc.) - and I mean EVERY last thing I could think of... Compression test - good to go, leak-down test - good to go, timing chain check - good to go, inspecting/testing fuel injectors - good to go, replacing ignition components (distributor cap, ignition pickup, rotor, spark plugs, spark plug wires, ignition coil - all ACCEL replacement parts, so a nice cap and rotor, with brass contacts, and quality plugs (properly gapped) and wires, just to ensure these were not weak links in the chain somewhere) - good to go... I mean, I have gone through everything that could possibly be a problem, only to find that everything else is functioning precisely as it should!!

The only reason I figured all this time, that it couldn't possibly be the ECM/PCM that I had purchased as a replacement for the one I took out to fix the crank, but no start issue, is because of the fact that, when I purchased it, and installed it into my Jeep, she immediately started up and began to run for the 1st time in what had been a 6 to 8 month period of time. I mean, it hardly cranked over but a few seconds before she started right up, just like she always had before, and seemed to be running like a champ... However, it wasn't until I began to drive it around a bit, that I understood that my battle was not over. Upon reaching operating temperature, it didn't matter what I would work on, and/or replace, the Jeep just would NOT drive properly once it got warm. Compression and leak-down tests showed that my cylinders were all in decent enough shape for a Jeep with 210000 miles on her. Not what you would want to see out of a brand new vehicle, no. But nothing at all out of the ordinary for a vehicle with some miles on it. Not to mention, even before testing, I had never known my Jeep to burn a bit of oil. Leak a bit... Sure. Who's 4.0L doesn't leak a little oil from some place or another?! That's no problem... Just keep it off any nice n clean driveways, no problem. But no leaks significant enough that I ever needed to top my oil off more than about a half qt, to maybe a full qt, between oil changes. Depending upon how hard I may have driven it at any given point in time. Which basically means, did I drive it with a trailer hooked up to her, or not? Anyway, no matter what I would fix, or replace, every time I would get back into the driver's seat, and take her for a spin, the very same thing would happen each and every time. It will reach operating temperature, and sure as the sky is blue and the grass is green, she'll just start misbehaving again, and exhibiting the same random missing/mis-firing, and all the bucking, and jerking, and terror that goes along with it, because for whatever reason, when these 4.0L engines get to missing/mis-firing, they definitely do not leave you with the impression that everything is going to be okay. Anyone who had never experienced it before, might very easily assume that what they were experiencing/feeling could be a transmission problem, or worse (though I'm not sure there's much else worse than a transmission problem...). The point is, when this motor is missing/mis-firing, you KNOW it! Because it bucks, and shakes, and makes some of the most terrible sounding noises, that anyone could get the impression that the entire vehicle could shake itself apart until you were left sitting in the middle of the road, buckled into a Jeep seat, with the rest of the Jeep laying there in pieces all around you... Okay, its not THAT bad... But it is bad, and I know I've experienced it enough recently, that if I manage to get this Jeep running right again, I swear I'll do everything in my power to ensure my ignition and fuel components are all up to par, and well maintained, so that I never have to experience the same feeling again. At least, not any time soon.

At any rate... I've replaced the CPS, the IACV, the up and downstream O2 sensors, and I made certain to purchase NTK/NGK components any time they were available, and when not, I went Denso. So I know the parts I'm purchasing are not the cheap bottom of the barrel crap that these 4.0s don't like, but instead, the quality OEM components, or close enough to it, that fitment, and/or tolerances are not an issue.... And finally, I came to the realization that I have come full-circle, and I've nothing left to consider, but the idea that I may very well have purchased a fluke ECM/PCM, which must have something shorted out or loose inside, or just bad in general, to where, when the loop gets opened (or closed, whichever is the one that happens when the engine has warmed up enough) upon reaching operating temperature, and control of the running engine is handed over to the ECM/PCM to keep it running, something in that little nightmare of a metal box is just not functioning as it is supposed to, and it's causing my Jeep - which runs BEAUTIFULLY from cold start, to the time this change in engine management occurs - to run like absolute garbage!! No 2 ways about it! And so, as soon as I finish writing this post, it's off to O'reillys Auto Parts, with receipt in hand, to remove the PCM from my Jeep in the parking lot, and exchange it for one that I am hoping against all hope, will FINALLY resolve my problem, and allow me a properly running Jeep, so that for the first time in WEEKS, I can hopefully return to work tomorrow! Because between trying to fix this Jeep, and NOT getting a paycheck every week... I'm about as broke as I could possibly be, and I cannot take it any more!

So... What I wanted to ask... Is if there is any type of vehicle-specific procedure I should be performing, upon the installation of this, the second ECM/PCM I will have installed into my Jeep, that I should be doing/performing, prior to taking it for a drive, in order to ensure I've done absolutely EVERYTHING I CAN, to end up with the best end result possible??? I mean, is there something I'm missing (no pun intended... No... Really... It's not funny anymore, and I'm about to lose my head if this vehicle does not run right after I install this ECM/PCM), or not observing, or doing properly, upon the installation of a new/remanufactured ECM/PCM, that I should be doing? Other than disconnecting the positive battery terminal, grounding it out to the negative terminal for 30 seconds or more, turning the key to the on position, but not starting the vehicle, turning the headlights on, turning the headlights back off, turning the key back to the off position, then starting the vehicle, letting it run in neutral till it reaches operating temperature (with the parking brake engaged), and finally, getting into the driver's seat, disengaging the parking brake, putting the vehicle into "drive", and then driving it at 40-45mph for approx. 5 mins or so, before taking it onto the interstate and pushing the pedal to the floor a few good times, to let her get up and go a few times? After which, it should be back to normal, everyday driving from there on out... Am I missing anything there? If so, PLEASE do leave me a reply to this thread and let me know whatever it may be, because as I said, once I finish writing this, I am going to the store to exchange my current ECM/PCM for a different A-1 Cardone remanufactured ECM/PCM, and I will be checking back here after getting it installed, just to see if anyone may have left any responses (for which I will be eternally grateful, have no doubt about that), prior to performing the above mentioned procedure, step by careful step, and hoping that, upon completing the process, that I might finally get my good running, reliable old Jeep back!

Thanks in advance to anyone who leaves any useful information. I assure you, no matter how small or insignificant it may seem. If you feel like there is something I could be missing somewhere, please let me know what it is, and I will absolutely be sure to give it a try! At this point, I'm on a wing and a prayer, and just hoping for some good luck with this Jeep for the first time in what's now going on a full year's worth of time...