I am at my wits end here guys (and gals, if any happen to stop by and read this) and I don't know what else to do! I realize that there are plenty of these posts, all with different titles, but concerning this same nightmare of an issue/problem, and I swore that I was just going to keep reading through existing threads, and checking stuff off my list, and NOT author my own post... But man, at this point in time, I just don't know what else I can do, and I've been out of work for a couple of weeks, because our other car blew a head gasket, and I am just not in a position right now to be purchasing a new or used vehicle of any kind or value, so my 1997 Grand Cherokee Limited 4.0L 2wd is my ONLY option, and I can't afford to just keep throwing parts at it either! So I'm hoping maybe if I describe my situation in particular, in a detailed enough manner, that maybe, just maybe, I might get lucky, and have someone check the post out, who can offer up some new suggestions/possibilities/insight which could lead me to possibly finally being able to get it back on the road and drivable (after it's reached operating temperature).

Several months back, my Jeep died on me in one of the tubes of one of our local tunnels here in Tidewater VA, and it sat for a while, because at the time, we just happened to have another running car, and I typically stay way too busy, between having a pretty big family, and working to provide for that family. At any rate, when I began working on it here and there, I was, like most guys, hoping against hope, that it was NOT my PCM causing the problem. It would turn over as great as ever, it just wouldn't start up and run. So I replaced the CPS, no luck. I replaced the fuel pump, and again, no luck. It wasn't getting spark or fuel near as I could tell. And when I finally purchased a scanner, and it wouldn't connect with the Jeep, I finally bit the bullet and purchased a PCM, and just like that, after months of sitting, she started right up, just like I told everyone who had been trying to tell me it was a lost cause, it would just as soon as I got the right part put in it. Well, it did indeed start right up, however, as soon as I went to drive it was when I realized that it wasn't going to be that simple. But, as luck would have it, now that I've got an operational PCM, I connected my OBD II scanner, and picked up codes for ignition issues, as well as a bad idle air control valve. So I replaced the distributor cap and rotor, plugs, wires, ignition coil, and finally the idle air control valve (as I'd already cleaned the one that was in there 3 or 4 times over, and I was pretty certain it was just done-zo), and man, it started right up, and I could tell before putting it in drive that it was running better than it had probably the entire time that I have owned it. FWIW, mine is at 210,000 miles, and since I have owned it, I have changed the oil faithfully at every 3500 to 5000 miles with Mobile 1 synthetic motor oil and a Mobil 1 or K&N oil filter. I have also kept up with my air filter, and clean it when it needs to be cleaned, and then re-oil it before installing it back into the box as it is a K&N air filter (not the aftermarket cold air kit, just the K&N filter made to be placed right in the same box as any other stock filter.

So anyway, I put her in drive, and I head off down the road, and I'm totally stoked, because my gas gauge is now functioning 100%, and I'm reading my voltage on the dash as well, and that's to say nothing of the fact that the rest of the work I'd put into the thing clearly had it running like an absolute DREAM! I mean, it felt so great that I couldn't believe it! And this went on for about a total of 10 minutes, before suddenly on the interstate, I guess my new functional PCM told the rest of the Jeep "hey, we're at operating temperature here folks", at which point, all my hopes and dreams came crashing down, as the Jeep began bucking and sputtering, and just having a difficult time due to what I could feel and smell was an obvious issue with fuel delivery. There was just too much fuel being applied when it did not need to be, and this was causing the cylinders to have a difficult time with proper combustion. So I pulled over, thinking, okay, I must have a bad upstream 02 sensor as well. So I disconnected the upstream O2 sensor, which I thought was supposed to put it in an "open loop" mode or something like that, which would quickly allow you to determine whether it actually was a bad O2 sensor or not, because if it was, I was under the impression that once the O2 sensor was disconnected, the Jeep should pretty much even out, and at least stop all the bucking and misfiring. But this did not occur. It kept right on bucking, and halfway acting like it might even stall out any time I had to stop at a light and get up to speed again. Once I would get up to around 40mph or so, the bucking would chill out significantly, but only if I was easy on the gas pedal, and kept it right between about 40 and 50 mph. And even then, it was still misfiring, just not as badly as when getting up to speed, or when trying to keep up to interstate speeds (which are 65 to 70 mph where I live).

So I'm at a loss at this point. My scanner is not pulling up any codes, aside from occasionaly the code that lets me know there is a misfire occurring, which it is very clear is the case without my scanner needing to inform me of it. I mean, this fuel issue, it causes this thing to act as though something catastrophic could very well be occurring. I'm not sure if it's the straight 6 orientation of the 4.0L engine, or what, but this thing feels TERRIBLE when it is missing on a cylinder, or misfiring for any reason. You definitely can't miss it. I've used quality remanufactured PCM by cardone, and decent champion OEM plugs, along with NGK wires, and NGK CPS, because I'd already read about all the nightmares continuing due to substandard parts. So I am just at a loss at this point. I've always got good pressure to the fuel rail, and hell, EVERY TIME, when its cold, it runs like a dream. Its only when it reaches opperating temperature that all the chaos begins to go on... I'm dumbfounded, and I cannot tell you how much I would appreciate it if anyone has any suggestions or help in general for me at this point. Also, I did go through before changing the PCM and clean, and re-attach all my grounds as well, on both the cable sides, and the grounding surface sides. So I know my grounds are solid as well. Any help would be greatly appreciated here. Thanks in advance!

 

I can’t really remotely help, you need a multimeter to do some testing on it , they are cheap and tests are easily done to eliminate possibility’s. Assuming the computer instal is good - the connections are known to move and cause issues- all mine are zip tied together to hold them solid.
the crank sensor and cam sensor could be giving iffy signals, just check connectors on the o2 sensors they can corrode . From my stand point I know the car relies a lot on throttle position inputs, it effects so much than other cars I have had - I have had terrible issues in this area having problems you described. I’ve actually narrowed it down to a dodgy throttle body and I have another one sat in a cupboard for next time this issue crops up.
also are the spark plugs gapped right ? They will run different hot or cold . Just some ideas . Best of luck 🤞

 

No man, thanks, really! Who knows, you may have helped a great deal. I know this is going to sound really stupid, as I think about it in hind sight... But I honestly just assumed that since I purchased the spark plugs after giving them specific info on my vehicle, that the plugs I purchased were just automatically gapped properly for my specific vehicle... And I'm not even kidding, or "just saying"... I genuinely just purchased them and installed them, without even thinking about getting a gap tool to go along with them, much less actually using it.

Additionally, I have checked the upstream O2 sensor. I unclipped it, and sprayed it down with electrical cleaner, and then put some di-electric silicone grease on the female connection and pushed it into the fitting (I have learned to do this with all of the connections on a Jeep anytime that I take one apart, as they are so tempermental when it comes to their electrical systems in general. Like how they are finicky with issues pertaining to resistance, as well as the tolerances in relation to any one of their sensors. A Jeep wants to see a given number for instance, not an "acceptable range" from this number to that. If the part is supposed to provide a resistance of 2 ohms, then the Jeep wants to see that 2 ohms, not a signal with a resistance that could fluctuate between 0.8 ohms and 3.2 ohms, which could allow it to function beautifully on literally ANY other vehicle), and only after doing this, and ensuring that the tines, or barbs, or whatever they are called - the little metal things inside the male ends of the electrical connectors/harnesses - on the male end of the harness, as well as each of the contacts on the female end of the harness as well, are ALL acceptably clean, will I re-connect the harness. Which I did.

However, I also have not replaced the throttle position sensor either. This is not the only sensor which I have not replaced either, there are several. Like the MAP sensor, and the downstream O2 sensor, just to name a few more off the top of my head. My point is, that I have not replaced everything, as I have at the very least tried to do my research, and to do my best to only replace parts which seem as though they could be related to the symptoms I am experiencing. From everything I read, it seemed to me that the TPS would be sort of barking up the wrong tree, but if you are saying that yours caused you troubles like I've described, then it is certainly worth a shot, so I will run out as soon as I have an opportunity and pick up a TPS and put it in there and see what happens. I guess the best thing to do, would be to just go ahead on and pick up an upstream, and a downstream O2 sensor when I go to get the TPS, and then install all three of them. That will take another fairly sizeable chunk of "what ifs" out of the equation, and I can just take her for a drive after that and see what I'm working with.

Just out of curiosity, is there any particular O2 sensor I should be buying? Same for the TPS really. Is there a particular brand I should be buying? I know that that these Jeeps like to have their Mopar/NTK crankshaft position sensors, and won't really settle for anything else but the OEM part there. Are the O2 sensors and/or the TPS the same way, or do I have a bit more leeway to purchase whatever they have on hand in store, as opposed to ordering them to make sure I get a certain brand. Thanks for the suggestions, and thanks in advance for any future assistance you might be able to give.

 

I’ve heard spend the money on throttle sensor and buy oem from dealer.
fyi I’ve had like six cheap sensors so 💁‍♂️

everything else I changed made no difference 😂

another common issue can be cracked exhaust manifold which then gives you supposedly false o2 readings . I am not sold on that theory though since my exhaust still travels down the pipe and gets read.

also after tps change it’s worth disconnecting the battery for half a day, then reconnect, it will run wired for a bit but the computer should relearn how to run and fine tune the engine with different sensors as no two engines and sensors are actually ever the same.

I had issues on a Pontiac for months before some garage said the plugs were gapped wrong, it was sweet after that - the plugs were installed by a different garage fyi !!! I do it all my self now

 

Again, thanks so much for your time. I really appreciate the responses. That is good to know about the TPS, because that would have been the one that I went cheap on if I had done so on any of the three. So, in an effort to hope I get it right this time, I will purchase all three of them by NTK if I can get them that way. I know for a fact that I can get the O2 sensors by NTK. I'm not sure about the TPS though, so if it turns out I can't get an NTK, I'll get a Dorman, or some OEM spec one that is on the pricey side of things. Either way, I just won't purchase anything off of Amazon. They had a "HICKS" branded upstream O2 sensor which was $24 and some change, that I have to admit, looked pretty enticing after I haven't been to work in a while. But for starters, it wouldn't have been delivered for like, 2, or even closer to 3 weeks. So ultimately, I decided that wasn't so promising after all, which was likely a good move, regardless of why it was made, or not made.

Anyway, yeah, so also, I'll purchase a gap tool at the parts store as well, and I'll take each of the plugs out and check them against whatever the spec is for the 1997 4.0L engine, and any of them that are not proper, I'll get them more proper-ized. See, and that is one of the weirdest things about this entire situation, is the fact that, none of the rough running, spitting and sputtering, occurs until my engine reaches operating temperature. But as soon as it does man, its like all hell breaks loose, and the PCM kicks in and starts trying to manage things, but the rest of the Jeep is just like, "hey listen buddy... we were doing fine without any PCM at all for however long it was we managed to keep on ticking until the last one of you guys died completely... so don't go thinking we're gonna just start listening to you at the drop of a hat just because you start barking orders around here!" And the way the truck feels, is like there are literally no two parts able to communicate with each other correctly, and it just starts acting like it wouldn't know how to run right even if it were brand new off the show room floor.

FWIW though... I was aware of the whole, disconnect the negative battery terminal, and let the Jeep sit for a while, thing. I've even been told to turn the blinkers on, and to turn the headlights and just different other stuff on, and then off again a couple times, in order to sort of aid in bleeding the remaining power/charge off of the system a little faster. But regardless, I give her some time before I put it back on and start her up. From what I've heard, this procedure is supposed to be done prior to driving the vehicle at all, any time ANY sensor is changed anywhere, regardless of the particular system the sensor may be a part of. And since I unplugged my upstream O2 sensor, and then did the whole "reset" thing (described above), I will say that, while it does still run sort of rough, I have absolutely noticed that it is not NEARLY as rough as when the O2 sensor is plugged in and the vehicle is attempting to operate in spite of it. So that has kind of made me hopeful that maybe, in the end, it might just be that instead of relying on unplugging an O2 sensor, in order to be able to tell if that is what is causing the issue, that I really just need to replace it all together, and once I have a new, quality sensor in place of the old one, who knows... Maybe after all this, I finally will be able to go and drive my Jeep on the interstate again, after which, if it drives well, I can finally return to doing some plumbing work and getting paid. Man, I can't tell you just how nice that would be!

 

Okay, so I finally got all the parts I needed. I got an ACCEL distributor tune up kit, which comes with better plugs than the original ones I purchased a couple weeks ago. It also comes with a distributor cap and rotor that have copper contacts, and better wires than the cheap-o ones I purchased a couple weeks ago as well. I got a brand new NGK throttle position sensor, an NGK downstream O2 sensor, and I could not find an NGK upstream O2 sensor - PartsGeek said they had one in stock, so I ordered it, but after I received order confirmation - after having paid for the parts and shipping - I then received an additional email a day later, informing me that the NGK upstream O2 sensor was NOT in fact in stock, and that they would be refunding me my money (which took 3 days after receiving that email to receive back on my debit card) which I had spent on the NGK upstream sensor. So, I then searched high and low for some store locally that might have an NGK upstream sensor, to no avail, so I ended up purchasing the ONLY O2 sensor that anyone around my area had, period, which wound up being a DENSO brand sensor. I installed the DENSO sensor immediately upon purchasing it from my local NAPA. Installed it in the NAPA parking lot. And today, the rest of the PartsGeek order should arrive, which will contain the NGK Throttle Position Sensor, the NGK downstream O2 Sensor, and the ACCEL distributor/ignition tune up kit, with the better plugs, wires, cap & rotor. So after I receive all the remaining parts, I intend to use the spark plug gapper I purchased as well, to properly gap each of the new plugs I will have received, after which I will remove the ones I had previously installed - none of which, had I gapped, just installed them exactly as they were straight out of the box - and then install the properly gapped ACCEL plugs, distributor cap, rotor, and new and improved spark plug wires. After that, I will remove the existing TPS, and install the new NGK one. Then comes the downstream NGK O2 sensor install, after of course, I remove the existing downstream O2 sensor. And that will be everything. FWIW, before I begin all this work, I will disconnect my negative battery terminal, and leave it disconnected for the duration of the time it takes me to install all these newly acquired components, so as to allow the Jeep to reset itself upon completion of these installs, and once I get the negative battery terminal re-connected, after which, I would be starting up, and attempting to drive my ZJ on the interstate for the first time in months. Because as I understand it, based upon the documentation received with the new IAC valve which has already been installed, it takes resetting the PCM, and then driving at over 40 mph constantly and consistently, for 10 or 15 minutes, for the PCM and all the newly installed components to sync up, and to begin functioning as they should. I assume this is a period of programming for the vehicle, and only seems archaic, due to the fact that I am dealing with a 1997 Jeep Grand Cherokee Limited 4.0l 2wd, which, for all intents and purposes, IS archaic by todays current standards, and has a PCM which does not have a super fast processor by any means, and so it takes it a while of driving the vehicle at that rate of speed or higher, consistently, in order for the PCM to recognize the newly installed components, and to then re-program the vehicle to operate based upon the improved performance provided by said components.

I am hoping against hope, that when I get onto interstate 295, right down the street from our house, that my Jeep will get up to speed (which is 70 mph), or at least let me get up to 65mph, at which point, I intend to switch on my cruise control, and ride the right lane for 20 minutes, or possibly even 30 mins. Assuming it allows me to complete this last step, I would then be finished, and the Jeep should be programmed, and all new components synced up and functioning harmoniously together, at which point, I should be able to take an off-ramp, then keep straight onto the on-ramp, which will place me back on 295, headed back toward home, and during this duration of the trip - assuming I make it that far - I intend to do a little more intense driving. I will put the pedal to the metal, and see how she responds, and see how fast I can get her going without experiencing any missing or misfiring. I will allow it to drop speed significantly, and then bring it back up to speed a few times, and just do some general "lets see if she will do this" type of test driving. And then I will bring it home and park it, and have a look under the hood, just to check and make sure that everything is okay.

Now, I do not even like to THINK about the alternative, which of course is, if I am to jump onto 295, and before even reaching the next upcoming set of exits, she starts bucking and missing and misfiring again, to the point that she begins to run so rough that I am once again concerned that if I do not take it off the interstate, it may stall out, or otherwise break down again, after which point, it has proven to be difficult to start up again at times. If it starts running that poorly all over again after installing all the new components, I will then be at a complete loss, and likely ready to phone our local vehicle scrapper to bring his tow truck by our house, and pick the Jeep up, and just get it out of my sight, and I imagine I'll just have to accept the fact that I won't be getting back to work anytime soon, until I can afford to purchase the best thing I can find for the most affordable price, whenever something like that is available, which is never soon enough. But at that point, keeping, and continuing to dump money into a Jeep that just does not want to seem to ever run right again, will likely seem all but pointless and hopeless to me. So, I will likely look into whether or not I can return any of the most recent parts purchases. The ones I can return, I will remove from the Jeep in order to do so, and the rest, along with the Jeep itself, will remain in the driveway only as long as it must, in order for the tow truck driver from the local scrap yard to arrive and tow it away, and out of my sight.

The only other thing I would think it may be at that point, is a possible issue with the new/remanufactured PCM which I purchased a while back now, but which I will still be removing, and taking back up to O'reilly's Auto Parts, in order to either return it, or to fuss at whichever manager is on duty there, until they agree to refund me my money for the part, or to help me in contacting A-1 Cardone, so that they can reimburse me for the $400+ I spent on that part. Even if it would be possible to get my hands on one that would function properly... Eventually... That is a game that I am no longer willing to play. At over $400 a pop, it is not reasonable - at least as far as I am concerned - to expect a customer to continue shelling out those hundreds and hundreds of additional funds, until they finally receive one which will allow the vehicle to function as it should. It just runs too well, prior to reaching operating temperature, for me to understand why on earth it would change up upon reaching said temp, and then begin to immediately run so terribly that it went from a nice and smooth, responsive ride, to absolute garbage within what is always literally, only a moment. If this should be the outcome, I just do not know that I will have the patience to go on. I have considered other factors, such as... Perhaps I should have pressure washed the interior of the fuel tank, prior to installing the new fuel pump that is on her now, and then re-installing the tank onto the bottom rear-most section of the vehicle. Perhaps I should have done so, and then allowed for a period of time long enough that I could be certain any remaining water left in the tank had been given ample time to evaporate, or otherwise dry up completely, at which point, I could have installed the pump, and re-installed the tank, without having to wonder whether or not it could still be an issue of too much debris sucked on to the tea bag type filter on the fuel pump, which could then, I guess, cause difficulty enough for the pump to efficiently and effectively pump fuel from the tank, to the fuel-rail, that I suppose it could be a culprit in this game of hide and seek. But, again, I refuse to see how this could be the issue currently, because, if it were, then I would certainly assume that this would be an issue which would show itself immediately upon attempting to drive the vehicle in any way, at any speed, and I would not find it to drive near perfectly when cold, only to switch up once at operating temperature. This would be an issue, like so many others I feel like, which would not, or should not ONLY prove to cause trouble for the Jeep once at operating temp. The proper gapping of the spark plugs, I would certainly assume should cause an issue from the very moment the vehicle is started up and begins to run. If a spark plug is not able to properly provide spark, it is not going to provide a beautiful spark when the engine is cold, and start failing to produce adequate spark upon reaching operating temperature. This issue would immediately show itself, and the vehicle would just never run properly from the get go. Perhaps I am missing something here - and I am admittedly, no certified Jeep, or any other brand/type of vehicle mechanic - but this seems to me, to be one of those things like my grandfather used to tell me about, where it is pointless to make it out to be any more involved or elaborate than what it is. Spark plugs providing adequate spark, is a pretty black and white process, without much, if any room at all for grey areas. They are either sparking, or they are not. The PCM assuming control of ignition timing, should not negatively, or positively effect the spark output from the plugs. The spark is either going to be produced, or it is not, I would think it should be no more an issue there, than the fuel pump should be, and so, that is why, as I said, I would have no choice but to scrap the Jeep, and hope to find something else to drive ASAP. Hopefully things work out, because I should be accepting delivery of this latest list of parts I ordered within the next hour or two, after which, it should not take me but about an hour or two following their arrival, to get them all installed to the point that I can then attempt to drive it again. So it looks as though today, or this evening, at the latest, is going to prove to be the final test. Here's praying I pass, and get this thing back on the road!

 

It was the best of times, it was the worst of times..

 

If your having the plugs out and spending time on it i would compression test while I am there. You never know

 

Find out where all the engine management grounds and refresh them if you haven't done so already.

 

I have done so on a few of them, but not all. As a matter of fact, just the other night, as I was finally installing all the additional parts I had received, I located what I assumed to be an additional ground wire that I had never noticed before. This one is attached to the engine block by the same bolt that secures the oil dipstick guide tube support to the engine block. As an aside, but still in relation to this very same ground, I happened to notice that a good two to three inches of the wire, at the end of the wire, from the crimped on eye connector which allows the bolt to pass through it in order to fasten it to the engine block, on down the wire, consistently for about two to three inches, this wire is actually stripped and all together bare. After that initial two to three inches at the very end of this wire, all the way up to the crimped on eyelet fastener fitting that the dipstick tube support is positioned in front of, and a single bolt passes through the dipstick tube support, as well as through the crimped on fitting on the tip of this ground, and then it goes into the engine block. It is toward the rear of the engine, on the passenger side, right around the same distance back from the front of the engine, as the oil filter. It's a decent distance back from where the distributor is located, further back toward the firewall, and the bolt fastens the wire and the dipstick tube support to the engine block, about half way down the overall height of the engine block, close to mid way down, but I would say a bit more toward the lower half of the engine block then quite dead center. Anyway, not only did I notice that this wire was there, but also, the good bit of exposed copper wire made it possible to see that the wire (at least, the portion of it which is stripped, and not hidden away beneath any sleeve/rubber/plastic) itself was not twisted up the way that wire typically is when you see it once it's been opened up. Instead, all the separate threads of copper which make up this one wire as a whole, are all running straight, each one parallel to the others, not twisted up or being held together at all. Additionally, the wire is pretty well coated in oil, and other debris, which I imagine is dirt for the most part, or just road grit and grime which has managed to stick to the wire due to the fact that it is reasonably coated with oil, or fluid of some kind or another. I couldn't say whether it is oil definitively. But that would be my best guess, as my ZJ is just over 211000 miles, and does leak oil minimally from more than one location, one of which, I believe is at the valve cover gasket, though I do not know precisely where. There is just a thin coating of oil which can be seen over quite a few different areas of the interior of the engine bay. One area which is clearly effected by this oil that is slowly, but constantly, or at least, consistently leaking, is the starter itself. I have long since noticed that it stays fairly oily, and because of this, it too has a good bit of dust/dirt/fine debris which coats it most all of the time. I have used electronics cleaner to clean off the areas of the starter where the electrical connections are located, but it never takes very long before those same areas are coated again. My Jeep has been this way for quite a while, and I had never noticed anything which I would consider a problem to arise as a consequence of it in the past. I have also owned three other Cherokees, and one other Grand Cherokee, each of which exibited this very same type of minor oil leakage. Or what I have always considered to be minor, as I've never had any problems or issues of any kind which I felt could at all have been directly (or indirectly for that matter) related to the very slow leaking of oil from any one component or the other. In my experience as a Jeep owner and enthusiast, (which has only ever gone as far as these Jeeps which I just mentioned, never any Wranglers or any other models aside from the Cherokee and Grand Cherokee. The Cherokee happens to be my preferred, or favorite model, and two of my three past Cherokees were significantly modded to the point of having decent lift kits, with rancho, skyjacker, or other decent enough components that their suspension, steering, and chassis mods consisted of. Aside from those mods which were not related to engine performance, or power in any way, I did have a few basic mods of those types as well, such as K&N cold air intake kits, throttle body spacers, or other very basic bolt-on mods/upgrades) Jeeps just leak oil, period. And you can be vigilant in efforts to spot and even repair leaky components, but in the end, by the time you get one minor leak under control and stopped, within a matter of days, or weeks at best, you are all but certainly going to wind up finding the next component to start up a small, often times very difficult to trace (unless you've invested significant amounts of money into purchasing case upon case of engine degreaser and brake parts cleaner. Because chasing down the origins of these such leaks, almost always requires at the very least, one can of one or the other, if not one or more of both), oil leak which you will find is originating from some other component, seal, or other part which is notorious for such small leaks in and of itself. In the end, I have always just made certain to maintain regular maintenance, at regular, or more than "regular" intervals, and to make a habbit of checking my oil level every couple of days or so, at which point I am always sure to pay close attention to the look and/or consistency of the oil I am viewing on the dipstick, and to even smell check it if I feel for whatever reason, that it is necessary. And as long as I am not finiding that I am having to replenish the oil in my engine at intervals which I would consider unacceptable, or otherwise indicative of some sort of bigger problem which could be going on, then I just maintain a proper oil level in my engine, and keep it moving.

FWIW, I do change my oil at regular intervals of 5000 miles each, at which point I will change my oil all together, draining all of the existing oil, and replacing it with new/fresh Mobil 1 full synthetic high mileage motor oil, and a K&N oil filter so long as I am able to obtain one, and when I cannot, I use a mobil 1 filter as well. My step-father taught me the benefits of lubricating an engine with Mobil 1 at regular intervals (more often than whatever Mobil 1 states is possible, depending on which type of oil you choose) as a kid, and its just a lesson that I have found on my own, stands to ring true as true can be, and so I continue to rely on Mobil 1 for my engine oil needs, and likely always will.

Anyway, I'm not certain what the ground wire I described above belongs to, and I have not yet removed it to clean it properly and re-install it to the engine block. But I did give it a really good cleaning with electrical spray cleaner, along with the surfaces of the block it attaches to, and the dipstick tube support which fastens to the block on top of the terminal connector crimped to the end of the ground I'm speaking of. I will take the time to properly clean it tomorrow. And if anyone could help me out with some info regarding just what specific component(s) belong to this ground in question in the meantime, I would really appreciate the help.

Lastly, I'd like to bring up the fact that, in spite of the fact that I am still experiencing the same symptoms over all, as I have been dealing with all this while, I can definitively say, that the symptoms definitely seem to have been significantly improved in their general severity, as well as their frequency. After getting all the most recent parts installed, I was able to get it on the interstate. However, after driving several miles at 70 mph, I got back off the interstate, because my Jeep seemed to want to start misfiring again. And one big thing about these types of problems, and/or their symptoms, in regard to my Jeep, or Jeeps in general, is the fact that, when these symptoms begin to occur, quite often they feel as though they could very well be something much more severe or catastrophic, like, say, a transmission problem. Because the bucking that is experienced at times, when these 4.0s get to misfiring and bucking and doing their little no spark dance, can not only be very jarring, but it can sound really bad as well. Any time my wife has been in the Jeep with me when this has begun to occur, she freaks right out. At any rate, I wasn't sure if it was worth mentioning that since that 1st drive I took. I have since taken it to pick up food, and to go to Harbor Freight, and to do a few other things like that, just right around our house, and I have definitely noticed that even when the engine reaches operating temperature, the symptoms I was experiencing all the time before, are only ever occurring minimally now, since I have driven the Jeep. What I am curious about, is even the paperwork which is included with a few of the components, mentions something about having to drive the Jeep at 40 mph or over, for a certain amount of time, in order for the PCM/ECM to be able to program itself to get everything functioning in general harmony. I would imagine this is the same for just about every part which I have installed. In other words, each of the parts I have installed, requires that the negative battery cable be removed from the battery for a period of time, in order that the PCM reset itself, so that, upon starting the vehicle, the ECM knows that it needs to program itself (so that it can manage all of the engine and transmission functions efficiently and effectively) in order that the vehicle can run properly. Okay, well, from everything I have read and researched in this regard, I have come to understand that the PCM that Chrysler used in these Jeeps is not only a relatively slow PCM/computer in general, but even by 1997 terms, back then they were considered to have processors which were much slower than many many other options which were available for use at that time. So, if that is the case, could it not be possible, that maybe my Jeep just has yet to have had the opportunity to run (or be driven) long enough, at high enough speeds, in order for the PCM to have effectively programmed itself? I mean, because if that is the case, it certainly would make a great deal of sense, seeing as how ever since I finished with these last installations, my Jeep literally seems to drive better and better, each and every time I start it up again, and go to drive it. So I have been curious as to whether or not I may be on to something there?

However, at the same time, it would seem that if that is the case, then while the Jeep wants for you to drive it at over 40 mph upon resetting the PCM, it also doesn't seem to like it very much if you take it onto the interstate and drive it at 70 - 75 mph. I assumed something is still wrong with it, but I am wondering if perhaps there is something like a break in time, or programming time, which is required by the vehicle to be accomplished, before it can establish an effective link of communication with the many different components and sensors. And if I have constantly failed to perform this "programming run" we'll call it, the way in which the vehicle wants for it to be done in order that it can successfully and effectively determine for itself, just the right amounts of fuel, air, and spark which will be required in order for the engine to run optimally, and for the vehicle to then be able to be driven either around town, or on the interstate with no problems.

So, to be clear, what I am asking, in short, plain english, is this.... Following a period of time during which I have completed any significant sensor, component, or other detrimental part installs/replacements, I do realize that I need to remove the negative battery cable from the battery in order to reset the PCM... However, is there some specific trick to the way in which I should be driving the Jeep following such service? I mean, does the Jeep require that I drive it at 45 mph, for 15 minutes straight (or ANY particular speed, for any particular time) following service of this nature? And lets say I am driving it at 45 mph, but I am hitting stop signs every few minutes, to the point that it is difficult for me to find a span of road upon which I can maintain a speed of 45 mph, for a period of time which is 15 minutes or longer. So, am I causing the PCM to have to re-start its entire programming process, each and every time that I come to a stop sign, or drop below 40 mph and have to bring it back up to speed? I have certainly never heard of anything like this before, and to be honest, it sounds/seems very peculiar and unusual to say the least. But, at the same time, I understand that my knowledge and expertise in this area, only go so far as my past experience, and whichever direction Google is able to point me to, after I enter a list of symptoms I am experiencing, along with the year, make, and model of my vehicle, into it's search bar, and take a look at the results, at which point, its still more or less a crap shoot. I'm no certified mechanic. Though, I will say that in all my 40 years, ,and all the different vehicles I've learned, and learned to work on and to properly maintain, THIS Jeep, is the very 1st one, which it seems I have yet to be able to repair to a trustworthy and fully (or close to it) functional status. I've never worked on a vehicle, that I was not able to drive it after the fact, and furthermore, to be able to trust in it enough, to not worry about it possibly leaving me stranded.

Any thoughts and/or suggestions regarding the issue of having to drive the Jeep at a certain speed, for a certain amount of time, in order to program it's PCM, will be greatfully accepted. Though, ANY thoughts and/or suggestions at all are just as welcome, and just as appreciated! And THANK YOU to all the individuals who have taken time out of their lives and their busy lives, to respond to this thread and offer up some help or direction. No matter how big, small, or significant, I truly am grateful for the time you guys have spent trying to steer me in the right direction.

 

What are the chances that I might have gotten my hands on a bad remanufactured PCM? Additionally, in what way could I check to ensure the one I purchased is in fact, the RIGHT one. At the time of purchase, I had the original PCM to compare it to. All the numbers matched up on the packaging, so I just took this to mean that I had the right part. I never bothered to actually match the numbers of the actual part up to the part I took out. Now, I have returned the original PCM in order to obtain the $ for the core charge, and when I returned the original PCM, I returned it in the box that the new one came in. (I know, I made a few really rookie mistakes there, but the damage is done now, and I am wanting to figure out if I can cross-reference my particular Jeep, with any numbering or lettering upon the current PCM I have in the Jeep, in order to insure I have the proper one installed) I am assuming if I purchased the wrong PCM though, that the Jeep likely would not even start to begin with, because it would not recognize the PCM to start with. Am I right in this assumption? Would it be worth it for me to take the PCM back to where I purchased it, and tell them that it is malfunctioning, and request a different remanufactured PCM in order to take it home, install it, and check to see if something that simple could be my problem? I have read so many nightmare stories about guys chasing down problems in these Jeeps, just to find out in the end, that a new part they purchased, and believed to be functioning properly - simply due to the fact that the part was new - turned out to be their entire problem. In other words, the new part they purchased was faulty, and so it never fixed their problem, which led them to continue chasing the issue, only to later find out that they had purchased a bad part from the get-go. As soon as they purchase the right part, or, a working version of the part in question, everything began to function exactly as it all should. Parts I have heard about this happening with the most, are definitely the PCM, and the CPS.

 

Will it start and run if you catch the throttle at the right time, before it stalls? Have you cleaned and inspected the throttle body yet? If the IAC is sticking or does not activate during start-up then it will stall.