chris71 Posted March 12, 2018 Share Posted March 12, 2018 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 More sharing options...
tacticleturtle Posted March 13, 2018 Share Posted March 13, 2018 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 More sharing options...
chris71 Posted March 13, 2018 Author Share Posted March 13, 2018 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 More sharing options...
Ωhm Posted March 13, 2018 Share Posted March 13, 2018 By-pass your fuel pump ballast resistor (if equipped), only to eliminate this as a possible cause. Link to comment Share on other sites More sharing options...
Eagle Posted March 13, 2018 Share Posted March 13, 2018 CPS getting heat-soaked. Link to comment Share on other sites More sharing options...
coolwind57 Posted March 13, 2018 Share Posted March 13, 2018 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 More sharing options...
coolwind57 Posted March 13, 2018 Share Posted March 13, 2018 10 minutes ago, Eagle said: CPS getting heat-soaked. He's replaced both CPS and Coil, both of which seem to occasionally have heat-soak issues for others. Is there a cause for heat-soak for CPS, other than a bad part? Exhaust leak, maybe? Link to comment Share on other sites More sharing options...
Eagle Posted March 13, 2018 Share Posted March 13, 2018 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 More sharing options...
chris71 Posted March 14, 2018 Author Share Posted March 14, 2018 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 More sharing options...
chris71 Posted March 14, 2018 Author Share Posted March 14, 2018 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 More sharing options...
Ωhm Posted March 14, 2018 Share Posted March 14, 2018 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 More sharing options...
Ωhm Posted March 14, 2018 Share Posted March 14, 2018 Yes, anything 4.0L. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted March 15, 2018 Share Posted March 15, 2018 How does the cps wire look? I've had one melt to the header and cause this exact issue. Link to comment Share on other sites More sharing options...
chris71 Posted March 15, 2018 Author Share Posted March 15, 2018 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 More sharing options...
Ωhm Posted March 15, 2018 Share Posted March 15, 2018 14 minutes ago, chris71 said: .....the two mopar ones are only putting out .02 , If you got the time, cruiser has the tip. Drill out the mounting holes and move CPS closer to trigger wheel. Cruiser Tip #7 Link to comment Share on other sites More sharing options...
87MJTIM Posted March 15, 2018 Share Posted March 15, 2018 34 minutes ago, chris71 said: the bwd cps puts out no volts BWD = Broken When Delivered Link to comment Share on other sites More sharing options...
coolwind57 Posted March 15, 2018 Share Posted March 15, 2018 52 minutes ago, Ωhm said: If you got the time, cruiser has the tip. Drill out the mounting holes and move CPS closer to trigger wheel. Cruiser Tip #7 I did that when I put my brand new CPS in a couple of Months ago. I also did Cruiser's CPS advance mod to it as well, found here: http://cruiser54.com/?p=127 Link to comment Share on other sites More sharing options...
chris71 Posted March 15, 2018 Author Share Posted March 15, 2018 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 More sharing options...
Eagle Posted March 15, 2018 Share Posted March 15, 2018 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 More sharing options...
88whitemanche Posted March 15, 2018 Share Posted March 15, 2018 Sounds like the ignition control module is finally on its last leg Link to comment Share on other sites More sharing options...
omega_rugal Posted March 17, 2018 Share Posted March 17, 2018 when it "dies", have you tested for spark? if not, suspect the CPS of course, OR as you say your ECU may be the problem too, also check the cps voltage right at the ECU, make sure it`s getting the signal... On 13/3/2018 at 7:28 PM, chris71 said: 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 the MAP sensor either works or doesn`t, and even if it doesn`t work the engine will start but run like crap since the ecu can not detect the changes in manifold vacuum, it is unlikely that it will suddenly stop working and the work perfectly again later... Link to comment Share on other sites More sharing options...
chris71 Posted March 18, 2018 Author Share Posted March 18, 2018 well i got another mopar cps sensor ,drilled the holes out and checked out put volts almost to .5 which is good from what i've read . checked out some more of the engine harness found a bad spot a factory crimp i missed awhile back that i didn't know about , the white plug to the icm has a green wire with a whit stripe on it the same wire had a break in it that was covered with tape anyways i fixed both places soldered and heat shrink , the idle smoothed out after , went for a drive for a few miles she acted up again but the symptom was different instead of dieing after coming back to idle at a stop it dieseled instead , no throttle responce turned the key off and tried to start again back to crank no start , unplugged the cps to check output volts still getting the same reading .493 at the cps plug ok thats good right , checked the tps it still checks good .8 and will rise and fall with the moving of the tps arm . probed the wiring harness for the cps all the back to the fire wall show a good reading . anyways after she sat for a few minutes started right back up running fine again like nothing happened . got home to check the stator with an analog volt meter to see if i was getting any needle swing while cranking and running seems to be ok , i don't have the tools to check the icm or the stator correctly . and i'm thinking the same as 88whitemanche that the icm is on it way out . and yes i checked for vacuum leaks at the intake mounting , the injectors , throttle body , vac lines , etc anywhere i could spray starting fluid to get a change in idle . so far no vac leaks found at this time . Link to comment Share on other sites More sharing options...
chris71 Posted March 19, 2018 Author Share Posted March 19, 2018 well i found the problem , it's the pickup coil in the distributor (stator) whatever you want to call it , it's getting hot and starts dieseling , i found after i shut it down i can take a couple ice cubes down inside the distributor for a minute or two but it back together she start right up and run fine for a few miles , so in the morning i'm ordering a new pickup coil to replace it with . so this adventure i have found out that i have 3 bad cps sensors , found some bad spots in the green/white wire going to the icm the white plug . and a bad pickup coil in the distributor ( not looking forward to replacing that lol ) . i think it might be as old as the truck if it is 31 years ain't to bad for a pickup coil . i have also learned you can't rely on an analog multimeter when probing the pickup coil wires looking for the needle to swing . if it's running the needle will swing and the volts will even read right till it gets hot . oh almost forgot the ecu i took out and replaced i took it apart and pulled the board out , it did have a cap at location c-12 that was deformed a rather large bulge on it's cylinder , the ecu number is ef8953005428 other than that the circuits and board still look like new , looks like i have research to do to find out what the capacitor at c-12 is for , Link to comment Share on other sites More sharing options...
omega_rugal Posted March 19, 2018 Share Posted March 19, 2018 4 hours ago, chris71 said: ooks like i have research to do to find out what the capacitor at c-12 is for trace it... and just to be sure replace all capacitors, they probalby fail soon after 30 years in service Link to comment Share on other sites More sharing options...
chris71 Posted March 19, 2018 Author Share Posted March 19, 2018 yeah it would fun to fix the ecu . haven't had the time yet to trace it down , i have a another one in the truck already , and the one i pulled out on the work bench , with both a chilton's and hays manual . i'll spend some time this week and trace it down . should be able to get some high quality capacitors for it online of course. Link to comment Share on other sites More sharing options...
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