i bought a 90 xj with a blow motor. replace the core with a 99 block and head.. used renix manifolds.

it starts easy and will idle as if it is miss firing on a few cylinders. (shakes bad and running rich) when giving it throttle it bogs down and wont go above the idle speed. after letting it idle it will backfire often and loud. im guessing it is when it warms up it is causing it to backfire. i relocated the CTS where the 99 CTS was (thermostat housing).

please help me! =(

 

Did you make sure the firing order is right? if its not your engine will shake violently.
get a fuel pressure gauge and make sure the pressure is around 39lbs.
if its not then it could be fuel pump going out.

mark

 

if all you used was the 99 block,I assume you used all the renix parts like flexplate,dist,etc. It sounds to me like the dist is not set right,I would try and retime it.

 

yeah i used all that. only the core cz the guy threw a rod and destroyed the block..

how do i go about resetting timing. i tried to get it right when i swapped distributors but i think i got it a tooth or 2 off =( imm searching on hw to reset it but no luck so far.

 

ok so it is controlled by the CPS. could be bad or not pluhgged in. im going to go look after the kimbo slice fight =)

 

The cps is plugged in or it would not start at all,but a cps going bad can cause this,but I think your timing is off from what you are describing.
If you can get a chiltons or haynes,but I will explain how to time. Pull #1 plug and place a rag in it tight,just tap ign until rag pops out,this will be tdc,make sure the balancer is at o degrees,your rotor should be pointing at the 5oclock position,or #1 on the cap,if it is not pull dist and replace it in the right position,a 1/4" either way from #1 will cause it to run bad,or not start at all,it has to be spot on.
The other thing to look at is the egr valve,if you bent the valve putting it in it maybe stuck open,make sure it is closed and that it moves.
Also make sure all your vacuum lines are right.

 

still not working right. same symptoms and timing is on. =( whats the possibillity it could be the knock sensor? when the motor blew the rod threw the side it could have jacked the sensor up also right?