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

[omega_rugal]

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...

[chris71]

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 .

[chris71]

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 ,

[omega_rugal]

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

[chris71]

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.