justjerald

***UPDATE***

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 what confuses me most is the fact its 180 degrees off with the timing marks lined up...

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

freegdr

which firing order did you goy buy the screw on the dist cap are in the wrong spot in one pic if that is what you based the firing order starting point by

freegdr

the top pic screws are in correct the bottom is correct

freegdr

bring motor up to tdc compressionj stroke dist on no 1 if your sure timing chain is correct you good, dist wont point to no 1 when timing chaing marks are ligned up valve timing and ignition are two seperate things

justjerald

its right but its still off i know its something stupid though but ive tried everything it wont work i have the manual for the jeep too so ive tried reffering to that but no dice

freegdr

which pic did you set the dist by

justjerald

number 2 bottom one

freegdr

you did compression stroke tdc dist to no 1 and firing order right

freegdr

you did not change flywheels did you,or different dist

squirellhall

check the o rings on the fuel pressure regulator or the regulatpr itself

justjerald

no i didnt same as it was with 4.0 in it

1988cherokee

does it backfire at idle too or just when you rev it up?

justjerald

at idle and it wont reve up

1988cherokee

ok I know you said your timing is right but timing is what will make it backfire at idle and not rev up. What you need to do is take the #1 spark plug out and rotate the engine untill you feel air coming out of the hole when there is no more air you should be at TDC then remove your cap and make sure the rotor is pointing at #1. Mine did the same thing when I pulled my dizzy out to reseal it from leaking and I thought I had it back in the right way but it wasnt and I checked it multiple times and it appeared right but as soon as I did it the way I just explained it ran fine, so its worth a try Cause it sounds like you might be off

1988cherokee

The other thing that could make it do what its doing is the crank sensor it could be to close or to far away, what you can do there is slot the bolt holes and put a peice of thin paper or card board on the the end of the sensor to get the right "air" gap between the flywheel and sensor