Jump to content

runs good for a few days then dies let it cool starts and runs good again


Recommended Posts

so the two months i have been having an issue where my 87 will run fine and all of sudden die . after letting set for a couple minutes it'll run fine for a few more days and do the same thing again. anyways it an 87 comanche 4.0l ax15 np231 , i've been through the normal suspects , so far i have found a bad dis cap and rotor(replaced) checked cps and coil replaced both replaced fuel pump bosch replaced , each time it got better but still dies? checked fuel pressure it is good . it has an 89 ecu in it wondering if it could be the problem , even went through cruiser's tips again . haven't replaced the fuel filter yet , doing that tonight after work , any suggestions as to where else to look would be great , i have yet to check the iac and tps . those are also on my list of things to check tonight .

Link to comment
Share on other sites

Check your fuel pressure rail. If you suspected a bad pump go to the bleed valve on rail and quick see the pressure at bleed valve and go from there. You can check pressure there and see if the rail needs rebuit. Many people have learned about the common fire from leaky injectors and poor fuel economy replace em and forget the pressure regulator on line( the roundish ball near the end of fuel rail by front of head near the fuel lines. I'm sure there is  detailed threads everywhere on it. If vacuum is good then regulator is good fuel pump etc you know and haven't spend a dime. Before sitting how long since you changed the fuel filter? Bad gas can cause this? Drop the tank and drain it from a rollover vent valve on top if it still has a factory tank. Its faster and easier and you don't waste a fuel tank gasket. Then change your fuel filter your talkn 1 to 2 hour tops and 10 to 15 bucks. Smell ur gas does it smell stale? Like old varness or stain?

Link to comment
Share on other sites

IAC is easy to take out and clean.  Should make it a lot better if that's the proble. Then just buy a new one.

 

I habe a 96 xj (OBD2) and it would do this once it got hot.  Was the crank sensor and the transmission bell housing.  If you have one pour coldish water on it and try to fire it up when it's messing up.  

Link to comment
Share on other sites

yeah all of that has been done , i have good fuel pressure , i keep two of everything cps , coil, tps, iac , coil/plug wire , discap rotor, all of which have been replaced tested even tested right after it dies all show to be good. my thoughts are leaning towards either ecu,map sensor or o2 sensor , replaced fuel filter and fuel pump relay last night , haven't had a chance to test drive yet . but i'm sure it's going to run fine for another day or two before shutting down again . icm could be causing a problem , the weird thing is it only takes less than 5 minutes to start right back up and run great for a couple days , took the ecu out this morning don't smell burned and i haven't seen any shorts on the circuit board or anything melted. i'm going to try one of the other ecu's and see if the problem persists , found some info on the map sensor last night on how to test it with a ohm meter and handheld vacuum pump to check voltage output . looks like i'll just have to keep testing , till i find the problem . 

Link to comment
Share on other sites

24 minutes ago, chris71 said:

yeah all of that has been done , i have good fuel pressure , i keep two of everything cps , coil, tps, iac , coil/plug wire , discap rotor, all of which have been replaced tested even tested right after it dies all show to be good. my thoughts are leaning towards either ecu,map sensor or o2 sensor , replaced fuel filter and fuel pump relay last night , haven't had a chance to test drive yet . but i'm sure it's going to run fine for another day or two before shutting down again . icm could be causing a problem , the weird thing is it only takes less than 5 minutes to start right back up and run great for a couple days , took the ecu out this morning don't smell burned and i haven't seen any shorts on the circuit board or anything melted. i'm going to try one of the other ecu's and see if the problem persists , found some info on the map sensor last night on how to test it with a ohm meter and handheld vacuum pump to check voltage output . looks like i'll just have to keep testing , till i find the problem . 

 

I feel your pain, brother.  i had a bad idle problem and it took me many weeks to solve it.  Good thing that came out of it is that I learned what those critical components do and I learned how to test most of them...and certainly learned how to replace many of them.  Analogy-wise, I went from Kindergarten to 10th grade in less than a year, as I've got only 7-Months of total Renix MJ ownership. 

 

And I feel that sometimes there's no shame in lock-n-loading the ol' parts cannon.   

 

Check battery/starter cables if you hadn't already.  Mine were a mess and I replaced.  Pull them to inspect, as I couldn't even see some of the worst areas of mine without doing so.   I hope you promptly find that it is something simple.  

 

Hang tough.  And by all means, please share when you find your solution.  

Link to comment
Share on other sites

I replaced the CPS in my '88 MJ. It was fine until about May, after which it would run for three to five miles, then quit. If I let it sit at the side of the road for 30 to 45 minutes, it would fire right up and I could drive it home.

 

Bad part. And mine was a factory Jeep part. It happens.

Link to comment
Share on other sites

i don't know if it's getting heat soaked , i have checked the exhaust and intake bolts to make sure they were tight , no exhaust leak in the area of the cps that i can find . fuel ballast would be a good idea but the 87 didn't come with one . it has a relay on the passenger side that was getting hot , i replaced it last night along with the fuel filter , the fuel pump i replaced a month ago, cause the old one quit on me out on the highway , after getting the new one in thats when this drives fine for a couple days no problems , then all of sudden just dies , let her sit for 5-10 minutes starts right back up , cps was my first thought so it was replaced with one a new i already had , few days later died again wouldn't start back up . walked to the parts store napa bought another cps and a coil , walked home got some tools and back to the truck , replaced both the coil and the cps again , kept the ones i pulled out , drove good for another week and started doing the same thing now it's every few days it'll die , anyways i put another ecu in today , new plugs plug wires , fuel filter and fuel relay last night , checked fuel pressure again just to make sure i was 39psi, sprayed some wd40 around all the vacuum areas i could get to no change in idle . i still think the map sensor is faulty or going bad , if i remember right the map sensor is part of the system to tell the ecu how much fuel is needed ( correct me if wrong ) also the only way i've been able to get it to die in my driveway the same way it does while driving is to pull the fuel pump relay out while it's running , bad parts do happen i've had my fair share over the years . i really need to go drive around and see if it happens again .  

Link to comment
Share on other sites

You said you replaced the cps. What brand? I ended up hunting down a mopar sensor for my 89 xj pukegoat cause the duracrap from az wouldnt work, same from advance, napa wanted as much as factory overstock online, I went to the junkyard $5 a magnet on a string in the bellhousing hole dangling around the mount and some brake cleaner and whala 1st crank. There was a ton of oil in there and metal shavings. It needed a thorough cleaning. Try it may work and doesnt cost much. I know my renix xjs hated any duralast sensor and would not run with em or if they did it ran like crap. I belive ive tried duralast crank, o2, and tps maybe and the crank and o2 were 2 for 2 garbage. I quite buying nonmopar sensors for any of my heaps after this. If I can't buy factory new I will jukyard pull a factory one.

Link to comment
Share on other sites

Your map is on firewall there is a vacuum line that runs to it. Unplug the vacuum it will die. You still havent said if you drained your tank yet. I thought bfore you mentioned the filter had not been changed and it sat awhile. Have you just disconnected your fuel line bfore filter smelled it yet and watch it drain for color or corrosion? Never mind I just reread the post " your last fuel pump died" you then stated "replaced it" so no ballist relay 87 relay is getting "hot". Trace the hot circuit. 

Link to comment
Share on other sites

If the problem started when the pump died and u replaced it. Then this issue started, I would try there. Check your sender housing where the wire is soldiered to the housing on the outside. Does it have good contact? Did it get disturbed when you changed pump? Try pulling the pump and running it out of a see through container. Maybe the new pump is drawing to much causing the heatsoak and shutting off at the relay. I never owned an 87 renix all mine were all 88' and 89's and 1 90. I didnt realize the 87s didnt have a ballast resistor and i seriously suspect that maybe why this is happening. They added it for a reason. If you have your old pump I would check info on it to current one installed. I'm sure by now your tired of messing with lockrings. At least they come off easy when new.

Link to comment
Share on other sites

well right now she is running good so far no problems , not really sure if it is fixed at the moment or not , i'll give it a few more days and see how it goes . thanks for the reply's i'll report back if it's good or bad . 

Link to comment
Share on other sites

17 hours ago, saveevryjp1998 said:

I didnt realize the 87s didnt have a ballast resistor......

 

1987 early builds had no ballast resistor. Ballast appeared later in the same model year. Pump noise complaint's.

Link to comment
Share on other sites

the wires look ok and not melted i did have that issue about 6 or 7 years ago melted the plug was happy to find that msd had the echlin plugs with pins so it was an easy fix .since then i've rerouted the wiring so its not near the exhaust , probed them to check for continuity as far back into the wiring harness as i could get . well she died again last night checked output voltage on the cps while a buddy cranked her over didn't show any output , tried the other two cps sensors and got a .02 out of them , so i ordered another mopar cps from morris 4x4 last night . the bwd cps  puts out no volts , the two mopar ones are only putting out .02 , so i'll have to apologize because i had hard time believing that all 3 were dead , but it is the only thing that makes since . but on a good note i've gotten really good at pulling the cps out lol, i have found that using a 1/4" drive 11mm shallow socket on a swivel with a small bicycle speed sensor magnet inside the socket works well , it keeps the bolts from falling into the bellhousing and makes it easier to start the bolts when reinstalling . of course break them loose with a 3/8 drive first, and finish tightening with 3/8 drive .

Link to comment
Share on other sites

lmao broken when delivered  yeah i'm thinking about doing that when the new one arrives , don't know if i want to try to advance it or not , but drilling the mounting holes to get it closer to the flywheel might be a good idea , 

Link to comment
Share on other sites

There was also a factory kit to delete the wires from the CPS connector through the harness to the ECU and install a new pair of wires that go directly through the firewall and to the ECU. Don't know if the kit is still available but it would be easy enough to make your own. It makes for a shorter run, which is supposed to transmit the signal better.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...