97 jeep grand cherokee problems
- Thread starter Kj413
- Start date
greg92jeepxj
Official Supporter
I'm going to hit the books on this one , can't let you suffer any longer . Will see what I can find . I cannot see you unhappy , not when we can do something about it. It's always something that needs to be traced or replaced but we'll get it . So very sorry ......
greg92jeepxj
Official Supporter
Yes , it's like running a desktop or laptop in safe mode. I'm not aware of any sensor that tells valve timing is too advance or retard but if sync signal from the cam sensor is out of range , this could contribute to loss of power , not to mention risk of skipping a tooth or two and run poorly and start hard or even not start. I'm preety sure the 4.0 liter is non-interference meaning a valve shouldn't strike a piston if valve timing is off or the chain skips altogether. Yiur engine has quite the mileage , do we know if a timing chain job was ever done ? I don't yet want to say that the replacement parts can be faulty as happens with these chain stores but will keep that in mind.
if anyone can check,for excessive slack in the chain , it may be helpful. Just remove the #1 plug and on TDC ( top dead center) , roll the pulley damper with a wrench or ratchet to see how much movement there is before the #1 piston begins to move. Should be very little to no slack. You can also do this with a timing light but will have to make your own marks as the 4.0 dosen't have any since ignition timing is only controlled by the PCM. Distributor is not adjustable for advance or retard. I would say it can't hurt to check this since it is not helpful to have poor valve timing. Hoping that this job was done already and we can move on in our diagnostics. Still need to gather research as to why this condition still exists but this is good to check. Your scan tool will be very valuable in upcoming diagnostics. I know your getting familiar with it , we will soon probably need to decipher some of what is jibberish to you and I . As far as dedication , I don't give up,until a rod goes through a block , heaven forbid , bite my tongue.
if anyone can check,for excessive slack in the chain , it may be helpful. Just remove the #1 plug and on TDC ( top dead center) , roll the pulley damper with a wrench or ratchet to see how much movement there is before the #1 piston begins to move. Should be very little to no slack. You can also do this with a timing light but will have to make your own marks as the 4.0 dosen't have any since ignition timing is only controlled by the PCM. Distributor is not adjustable for advance or retard. I would say it can't hurt to check this since it is not helpful to have poor valve timing. Hoping that this job was done already and we can move on in our diagnostics. Still need to gather research as to why this condition still exists but this is good to check. Your scan tool will be very valuable in upcoming diagnostics. I know your getting familiar with it , we will soon probably need to decipher some of what is jibberish to you and I . As far as dedication , I don't give up,until a rod goes through a block , heaven forbid , bite my tongue.
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greg92jeepxj
Official Supporter
Thanks . A good timing chain set shouldn't be too much but I don't know what your finances look like , not to mention , you've mention you've spent $$ already, I realize. I'm still wishing the best and still believe in a girl and her jeep.
greg92jeepxj
Official Supporter
I'm hoping for you that the timing is not an issue. Hoping to diagnose what is already installed before any new parts are installed. I try to stick to diagnostics but sometimes a parts needs to be swapped in to test. Some parts are not easy to diagnose like a mass air flow sensor for instance.
Parts like that need special diagnostic tools. Thankfully , your jeep is not in that category .
I am building on that code reappearing to further my research . I could just say let's check battery connections and clean grounds , which are important , I just think in this case we need to find something we may be missing or overlooking. That's why I put in my signature those very words. I believe in proper diagnostics , just find this a bit uncommon as you do. But I still try to treat this like a short in a wire , just got to find where and the fix is evident. Hanging in there too.
Parts like that need special diagnostic tools. Thankfully , your jeep is not in that category .
I am building on that code reappearing to further my research . I could just say let's check battery connections and clean grounds , which are important , I just think in this case we need to find something we may be missing or overlooking. That's why I put in my signature those very words. I believe in proper diagnostics , just find this a bit uncommon as you do. But I still try to treat this like a short in a wire , just got to find where and the fix is evident. Hanging in there too.
greg92jeepxj
Official Supporter
i know the feeling , I spent last November on top and below a pontiac grand am 2.4 liter OHC on a water pump job in the rain under a leaking canopy for two weekends . But sometimes we just got to take a break , rest and start again when we catch our breath. But yeah , I will be under or over another car or can again soon. Good thing I finally installed the transmission line on my jeep . It just dosen't end but when they're running , they're great !
greg92jeepxj
Official Supporter
Please be careful though , if running in open loop continuously , it will run rich and the catalytic converter will get hotter than normal , especially at idle. Don't mean to rain on your parade , you get enough in Washington state , just wouldn't want more trouble for you $$.
greg92jeepxj
Official Supporter
Have been researching probable causes why the P1391 code is setting . We already know it pertains to CMP (cam) and CKP (crank) but was also mention which is not surprising about slack in valve timing. I know where we stand with that . Was also thinking a worn distributor but that usually results in rough idle/ stalling and in extreme cases , no start. As it stands , your PCM has no trouble finding the DTC 1391 . Rather than think worn distributor , I would concentrate diagnostically on valve timing. To update , I incorrectly posted there are no timing marks on the 4.0 liter engine. There certainly are ! I verified that on mine. I just never refer to it as timing is not adjustable as previously posted. Sorry for that . I was celebrating my success to fixing the leaking high pressure trans line on my '92. All better now , thank you. The jeep as well.
What I will suggest ( trying to give free advice $$) is when this timing chain slack test is performed that the distributor cap be removed and note if rotor tip out of position with crank movement. I'm sure it's installed correctly if was removed for CMP sensor repair or the jeep wouldn't run. I wouldn't attempt to advance distributor timing to compensate for timing chain slack as it is likely to make things worse . Not only am I thinking DTC code but am also focusing on the actual drivability glitch your experiencing . It's around the time the trans shifts into overdrive . I'm not yet faulting the trans control module since this is at this time thinking out of the box. Thinking more that it's rpm related. Trying not to think too much and just focusing on the valve timing error possibility. As long as the PCM is feeding both crank and cam sensors 8 volts and the ground is good , valve timing slack is my hypothesis / prognosis , call it what you will. Also being sensitive to your dwindling funds as well. If all that is wrong is a worn timing chain set and tensioner , aside from $$ , hoping there is closure and you'll be cruising , smiling and blasting tunes in that order. Well , it's Father's Day and wishing a happy to the fathers in your life and hoping I'm on to something . I always believe in fixing the obvious before moving on diagnostically or further checks and testing are fruitless. Visual inspection such as damaged wiring or any noticeable damage and wear goes without saying. I hope this helps and still hold hope that you'll be able to drive your beloved jeep soonest . Feel free to look for any live stream data that may seem related . For example , sensor signal voltage and reference. I know I've just thrown a lot at you but approaches methodically and in steps , justice will prevail. I know , diagnostics are fun . Most think you have to be sadistic or without a life to focus on these lengthy procedures but I've actually accomplished successful trouble shooting before within my understanding and believe anyone with proper equipment ( computer safe test light , computer safe digital multi meter , a scan tool is nice ) can do this with nothing more than good reference ( shop manual ) and intuitiveness . Whenever I have a problem which prompts me to throw the nearest wrench at the nearest standing object , I know its time to drop it for now and father a new stragety . Wishing you well and lighting a candle and a Hail Mary all will be well soon. Greg
What I will suggest ( trying to give free advice $$) is when this timing chain slack test is performed that the distributor cap be removed and note if rotor tip out of position with crank movement. I'm sure it's installed correctly if was removed for CMP sensor repair or the jeep wouldn't run. I wouldn't attempt to advance distributor timing to compensate for timing chain slack as it is likely to make things worse . Not only am I thinking DTC code but am also focusing on the actual drivability glitch your experiencing . It's around the time the trans shifts into overdrive . I'm not yet faulting the trans control module since this is at this time thinking out of the box. Thinking more that it's rpm related. Trying not to think too much and just focusing on the valve timing error possibility. As long as the PCM is feeding both crank and cam sensors 8 volts and the ground is good , valve timing slack is my hypothesis / prognosis , call it what you will. Also being sensitive to your dwindling funds as well. If all that is wrong is a worn timing chain set and tensioner , aside from $$ , hoping there is closure and you'll be cruising , smiling and blasting tunes in that order. Well , it's Father's Day and wishing a happy to the fathers in your life and hoping I'm on to something . I always believe in fixing the obvious before moving on diagnostically or further checks and testing are fruitless. Visual inspection such as damaged wiring or any noticeable damage and wear goes without saying. I hope this helps and still hold hope that you'll be able to drive your beloved jeep soonest . Feel free to look for any live stream data that may seem related . For example , sensor signal voltage and reference. I know I've just thrown a lot at you but approaches methodically and in steps , justice will prevail. I know , diagnostics are fun . Most think you have to be sadistic or without a life to focus on these lengthy procedures but I've actually accomplished successful trouble shooting before within my understanding and believe anyone with proper equipment ( computer safe test light , computer safe digital multi meter , a scan tool is nice ) can do this with nothing more than good reference ( shop manual ) and intuitiveness . Whenever I have a problem which prompts me to throw the nearest wrench at the nearest standing object , I know its time to drop it for now and father a new stragety . Wishing you well and lighting a candle and a Hail Mary all will be well soon. Greg
greg92jeepxj
Official Supporter
Thank you for your update . I really don't have any experience with using sea foam and will be curious to its results as you will. I use RESTORE at oil changes and have been for any vehicle I've owned and it seems to keep compression healthy. But I don't know what else on the parts stores shelf is good for our jeeps,engine aside from Lucas . Opinions differ. You mentioned resetting the PCM . I'm familiar with re flashing which makes certain that all sensors are read in the proper range and ignition and fuel injection timing are correct as well as emissions equipment . There may be more as well but those are the big ticket items for the PCM. It's still confusing as to the actual glitch but an ociloscope would know better . The heart breaker is that sometimes even the PCM does not see what actually is wrong , it just sees the after effect. It may , for example be feeding the ignition coil(s) proper voltage but if the coil is bad only a miss or lean condition will show or spark knock and lead us to believe vacuum leak , bad O2 , knock sensor , etc. It is unfortunate that the only way to evaluate a driveability problem is to exhaust time consuming diagnostics . But this is the tried and true way to find the problem. I'm hoping as well that the "reset " done to your PCM will keep your jeep happy and you as well :grin:
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