ok a few years ago i had this car and had this problem. back then we all went around the pole trying to figure it out, i wound up just selling it but this past weekend believe it or not i wound up getting it back. just a glutten for punishment. anyway i'm bound to figure this out but need some expert help.

before i did about everything and did not seem to find it before i sold it so now lets see if any has since figured it out. today i started testing agian this time i ran the engine at idle and i connected a tach to the coil and i back probed the map signal wire. here are the numbers i had. so if someone has the numbers a good one show maybe can tell me if these are good or junk. i also noticed i had a time with trying to get the engine to idle smooth aor at least the tach show a bad misfire until around the 1000 rpm speed. here are the numbers.

ok here is the numbers with the engine running and back probing the map signal wire. also this go around i had a real bad what sounds like a misfire. i never ran the engine a these speeds trying to hold it steady for testing so i never noticed it. but i had a time trying to hold at the speed i show. if the rpm is blank it means i just could not get the tach to hold at the indicated rpms it may be the gage and may be the engine but the engine runs smooth. maybe need to toss in a pickup. but reading up on the lean code 51 i read about the pickup is optical and maybe it is dirty and causing some steady readings so i will take it out and see and clean it needed.
all numbers are rpm's and then volts at the 20 volt scale
600 1.23
700
800
900
1000 1.15
1100
1200 1.01
1300 1.08
1400 1.04
1500 1.02
1600 1.06
1700 1.04
1800 .95
1900 .92
2000 .88
that is the best i can do. so maybe i got bad map sensors from rock auto. this go around i will get a mopar map and go from there if the reading look bad. i don't know any other way to test them. i may do the 87 the same way later to see if it shows the same numbers. if they are different then i may have a bad map. again.so look these over and tell me if you can if they look wacko to you. or maybe someone else can tell me. thanks bp


i went out and tested the 87 2.5 the same way and this is the numbers on that car blank means could not hold stedy enough for a reading on the meter
700
800
900 rpm's above this
1000 1.74 volts
1100 1.69
1200 2.09
1300 2.06
1400 1.98
1500 1.84
1600 1.60
1700 1.58
1800 1.46 volts

 

https://www.2carpros.com/questions/1...-light-code-51

 

yep that was me. they did not help to get it back then and i was at the getting another ecu. but i may have missed something and that is why i wanted to revive this one. just in case someone else had this issue and found the cure. or maybe even another chrysler model had it and it got fixed.

that is why i started to run the testing all over. i did not do the map testing before i just replaced them but it looks like i may have got bad or incorrect sensors before. so now doing the testing and showing the results may help more. i did the map voltage test and posted the numbers so you might see them and say go or nogo. if they look good then the ecu is the next step as i did all the rest years ago. if the ecu fails to fix it then i will look for another harness and just keep going until i find it. but will post all testing and parts installed so others with this issue can see what i did again and may help them. thanks bp.

 

today i did a running test on the 02 sensor. i back probed the signal and heater wires and ran the engine. after about 1 min. the heater voltage dropped out and the signal kept going it was in the 70 mv range on the 200mv scale every min. or so it would spike up to 190 mv and then back down to 70 mv. after 10 min. it set the mil. i let it cool for 4 hours and did the test again this time the heaters never turned off and after about 5 min. it set the mil again the signal was around 70 mv and spiked to 190 mv . but now i'm leaning towards the map i have one on order and after i get it installed i will run these tests again to see if the numbers change. i have video on dropbox for interested partys

 

BEFORE you get all wrapped up in electrical tests to try and narrow down the fault. You reported that you had POOR IDLE and code 51 ...BOTH signs of an EGR hanging open problem. Actual EGR valve or Vacuum transducer. Had that problem with an 87 3.0 grand caravan!

 

i will look into the egr, tell me how man miles did you have on your car before you have egr valve issues. this particular car had these issues when it had 60,000 miles on it. and i believe it had them way before that. just some back ground on this car.

i have not tested the egr on this car yet on this go around but last time i did and it checked out but 7 years ago i may have missed something. so today i will remove it and see if it looks like it is working and see about testing it again. i may have missed something way back then. thanks. bp

 

found the issue and i believe it is repaired now. time is going to tell.

 

Going to leave us hanging until you feel the time is right to tell? Diaphragm operated items can go bad at any time, it's not a set mileage thing. And I've worked with and on so many cars that mileage when had a part fail is the last thing I would remember. LOL

 

for now no, i'm not saying yet until i prove it was the fix. thanks