87 Renix MPFI junkyard swap onto 4.2L CJ

[Mike CZJ]

I'm sure you have all seen and answered a post like this... but anyways heres my situation...
I have swapped a Renix MPFI system onto my 4.2L. i used the 4.0L head. i mounted the CPS on my bellhousing and used a 4.0L flywheel. now heres my problem. the engine does start and idle almost perfect, but when i go to rev it up, it sputters and misses bad, then when i let off the gas, it returns to an almost perfect idle. i got another throttle body with all the sensors and swapped them, (since i thought it might be the TPS) still no fix. i have 3 new injecters and the other 3 tested out good and are working properly. could it be the fuel presure (or lack of), could it be the distributer isnt advancing and retarding properly. what is the timing supposed to read with a timing light? (i know you cant adjust timing cuz the distributor is computer comtroled, just want to make sure i'm in the right area) any other ideas?

thanks
Mike

 

[mtbkr]

I would check the fuel press first you will need to maintain 35 to 40 psi
The other things I would look into would be the map sensor and crank position sensor

 

[RichP]

Fuel pressure for sure, that mech fuel pump supplies maybe 10 lbs on a really really good day. Did you change the whole thing, computer included.

 

[Mike CZJ]

swapped everything over....the only thing that is not from the XJ is the fuel pump, its out of some Ford (thats probably the problem, i hate Ford) it puts out 45 psi at the last time i checked.
how would i go about properly adjusting the CPS?

 

[techno1154]

You could also have a timing problem; ignition and or fuel injection. I am no expert on computer controlled engines so I cannot be very specific. However, someone one this board should be able to help you trouble shoot the problem. You may try posting on the OEM forum.

 

[Mike CZJ]

You may try posting on the OEM forum.

i originally posted this thread in the Modified Tech section but someone moved it..... strange considering the system i'm using is off an XJ...:dunno:

 

[CheapXJ]

the distributor is off by a tooth.