i just rebuilt the motor to a 4.6 stroker renix but now it wont run right it backfires and stumbles and pops out the rear like the timing is off but it is not. with the timing marks lined up and the distributer at the 1st spark plug its 180 degrees off so i fliped it 180 degrees and it fires up but does all the backfiring nonsence so i have redone the timing 4 times just to make sure i also have done a compresion test all the valves are opening and closing correctly the cps has been changed new wires new plugs new cap new roter and cylinders 1, 3, and 6 have no spark

so here are things ive done a buddy of mine has a renix xj as well so we decided to swap a few parts to see if we could fix mine computer and ditributor map sensor have also turned the distributor one tooth at a time to see if could find the right timing but same issue

what i have and have not done on this build
pistons h802pc
cam stock
new lifters
reconditioned crank from 89 4.2 light crank
352 conecting rods
new melling oil pump
24lb injectors
cloyes double roller if it makes a difference

parts i reused all i did was clean them
head
intake manifold
exhaust manifold
throttle boddy

 

did it do this b4 new cap?????

 

 

yup put it this way i put the motor in in january ive been trouble shooting ever sence i havnt drivin my jeep since november i miss so much and i have a baby due in july and i really want to drive my son home in the car i plan on giving him as his first...

yes it did it befor the new cap

 

was the correct year flexplate/ring gear used 87 thru 90 are different from all others being a renix jeep

 

Yup same one I took off my 4.0 renix

 

Same thing happened to me almost to the letter. After indexing the dizzy 4 times I got my 99 fired up but ran lousy also. I checked the vacuum presure at the intake manifold and found lots of leakage. It was a bear but I got under and managed to tighten the intake and exhaust, it ran much better after that but it still alittle rough. Now I have no spark at all at the plugs or the coil... Ive changed and just tested the Crank Position Sensor and its fine, I dont know where to go from here...

 

8 years ago.