engine code and running like crap

[giorno71]

i did a motor swap from a 2.5 to a cherokee 4.0 ho  in my yj now i have a code 73 and 75 and cant find info on them. jeep ran great for about 2or 3 months and now i cant drive it . it it started sputtering at arround 100 degrees now it dose it even when cold  i have changed every sensor i can find  cap rotor and wires and a new fuel filter . i did swap in a biggert fuel tank from a yj but used my pump and sending unit, just changed the float arm to the longer one .
now the rpms will fall to almost stalling but dosent then reves up and back down to almost stalling. if im driving and it starts to sputter the rpms dont change if there at 2000 they stay at 2000 but lose all power also the air intake soundes like its a scraping noise and really loud when it sputters  but when it goes back to normal so dose the intake  



Any ideas would be a big help

[giorno71]

the doner was a 92 into a 94 yj  using the doner ecm. the codes are from the on board code check.  when it was in the cherokee it hade no problems and no codes. i had taken the cherokee on a 6 hour road trip befor the swap and not one problem arose

[WhiteOut]

Sounds like the CPS

[giorno71]

swaped out the cps and wasent the issue  my buddy acually put mine in his jeep and it ran like a top

[frenchy]

Did this issue start right after swapping to the larger fuel tank, or was that done originally and ran fine with it?

[BlackYJ]

Here is a link for the YJ codes, http://www.jeephorizons.com/tech/yj_codes.html and as mentioned there is nothing for 73 or 75.  Did you count it correctly?

[giorno71]

yep read the code right even checked twicw more just to be sure. also how do you erase the codes from the pcm i disconected the batt but it didnt work. the wiring is the stock 2.5 wiring. icant seem to find the plug for the code reader either

[WhiteOut]

There is also no codes like that for an XJ.  Are you using the key on,off trick?

[frenchy]

Put gas in it.

[giorno71]

yep  using the key thing  and there is over half a tank of gas in it

[SwampSinger]

yep  using the key thing  and there is over half a tank of gas in it

go to Autovalue,.. borrow thier OBD2 reader and get the real codes

[giorno71]

yj and xj wiring harnes is virtualy the same the only differance is i had to change two ends on a couple plugs and wire in the two more cylinders, and that was it . it fired right up and like i said it ran great for a few months with no issues and its my only vehical so i drive it every day.  i dont have a autovalue here in medicine hat so thats not an option.

[BlackYJ]

yj and xj wiring harnes is virtualy the same the only differance is i had to change two ends on a couple plugs and wire in the two more cylinders, and that was it . it fired right up and like i said it ran great for a few months with no issues and its my only vehical so i drive it every day.  i dont have a autovalue here in medicine hat so thats not an option.

Any auto parts store should scan your jeep for free.  Try Crappy Tire

[BlackYJ]

Hmm... is the wiring the same between the YJ and XJ? As I kinda followed along, I got the impression it's the 2.5 YJ harness with the 4.0 XJ motor and ECM... could that have something to do with it?

Pat, I have the exact same setup in my YJ.  The bulkhead connectors to the firewall are different, so it is easier to wire in 2 more cylinder than to try and change the connectors

[BBD]

not sure if that year has them. but how do you O2 sensors look?