Problems with new engine, stumbling and backfire

Alright, so I got a new rebuilt engine, put it in and finally got to start it up. It took a few cranks to get started but eventualy did. Then I brought it up to 1500 or so and If I go higher it starts to stuble bad and will backfire. I thought the timing was 180 off so I changed it. With it like that I can not even get the engine to start. any ideas?

Thanks,
Kevin

My early XJ, 88, has a whole lot more possiblities than 180 out, can install the distributor in a bunch of wrong positions.
Put a compression gauge on the 1 plug and turn it over until, you get pressure. Line up the timing "0" mark on the balancer (easier if you chalk a mark on the front of the balancer)( always last turn to "O" to the right to take the slack out of the chain). Turn the oil pump slot until it lines up and install with the distributor rotor pointing towards the "1" mark on the cap (close or slightly after). The distributor kinds of twists, some as it goes in, sometimes hard to get the oil pump drive to line up in the slot. With a long screw driver you can turn the oil pump drive (slot) to close to where you want to be. A little trial and error, will get the shaft and the pump and the "1" mark lined up (near enough). With the 1 cylinder at the top of the compression stroke.

Switch the distributor back the way it was. Your problem at higher rpms is most likely a throttle position sensor or a MAP sensor.

Take out the distributor, turn the #1 cyl to TDC, put the distributor in at the 4:00 position, the trailing edge of the rotor should end up at 5:00 (#1 position on dist. cap). Try starting it, it should crank right up. If it does'nt try pulling the dist. out about 1" and advance or retard the rotor one tooth on the cam gear. Good luck!

the dist was in properly the first time but not set properly.there is a certain method , described in an old tsb. first set the engine up on #1 cyl. the timing mark on the harmonic balancer lines up with the decond mark from the bottom of the index marker on the timing chain cover. then you want to line the trailing edge of the dist. rotor with the trailing edge of the #i pin under the dist cap. you are spposed to have a donor cap to cut a "window" in the cap so you can see. also the ears on the dist that keep you from adjusting it need to be cut off so you can turn the dist enough to line up the rotor in the cap. everytime we do engines on 4.0's we set them up like this and dont have any problems with bucking or missing.

I did the mod. discribed by Jneary on my 88, worked for me.

I have been playing around with this for a while now, with no luck. I know I had it set at TDC on the compression stoke (#1 cyl). And thats how I got the engine to start and it would stumble and backfire. tomorow Im gonna go buy a new cap so I can try and get the dist set correct.

Since gettin it to start like that once or twice, I havent been able to again. I did advance the rotor and was able to get the engine to start (quickly) but it would not rev and would die within the first 5-8 seconds. Could it be a fuel delivery problem?

Im starting to get very agnnoyed with this. Hopefully cutting the window with a spare cap will work.

Thanks,
Kevin

the distributor has been moved too much. there is no adjustment, only an exact setting for best performance.

I am aware that there is one correct setting. I thought I had the right setting, I had it where everyone was describing (or at least I think i did). Im just fed up for the night. There may just be something stupid I just keep overlooking.

The procedure jneary is describing is called "indexing" the distributor, and it almost always resolves the kind of complaints you are describing. Be sure that the number 1 piston is at exactly top dead center on the compression stroke. Then align the rotor to the cap the way jneary described. Actually, according to the TSB the rotor should be just clear of the contact post in the cap, with an air gap of 0.020". The reason for cutting a window in an old distributor cap is so you can slip a feeler gauge in there and confirm the gap.

Be sure you have that clear. The rotor turns clockwise, so the TRAILING edge of the rotor should be just BEYOND the contact in the cap. As he said, if you can't get it to that adjustment by moving the drive one tooth either way, pull the distributor and grind off the locating ears so it can be turned to make a more delicate adjustment.