i just installed a rebuilt motor in my xj and it running rough barely idles if at all. i installed new motor mounts,flexplate,& header. i cleaned air idle control on throttle body, as well as a new one. checked fuel pressure at rail. tryd new cam sensor in distributor. new crank sensor in tranny. checked all vaccum lines,listened to injectors with thesiscope. checked timing several times.checked compression all over 100lbs . i drove it 2hours before i pulled motor & it ran great 3 weeks ago. put motor back in and now the what id call a floating miss, like a bad vaccum leak. anyone have any ideas or thoughts,am i forgetting something? :b angin:

 

have you narrowed it down to a certain cly yetdid you remove the dist

 

Long shots:

Wires may have broken internally upon removal?

Rotor OK?

New plugs, properly gapped? No cracked insulators?

Wires in proper firing order?

Engine properly grounded?

 

i painted motor but first thing this morning i pulled the grounds n scraped them for good contact. i replaced plugs, wires, cap & button,waterpump,when i slid motor in 2days ago. cant narrow it down to one cylinder hence what i call a floating miss. can pull any plug wire & theres no differance,same with injectors. i did get a factory defect cap & or rotor.apon first start up it sounded rough so killed it pulled plugs,looked all same. pulled cap and the button in the top of cap fell into the rotor, so i put the trail rated (old ones). which the old cap & button looks new themselves. i actually sprayed starting fluid around intake,its not suking in air anywhere. checked all vaccum hoses several times. i havent tried new maps, i did pull the vaccum from it with no change. this and computer are the only things i havent tried a differant part. injectors could be dirty but it ran like a champ before i pulled motor. injector o-rings are new.

 

it ran fine b4 you didi the plugs and wires

 

did you refer to a manual when you put the wires on or did you replace one at a time

 

it ran fine before i pulled motor, not so much after slid it back in. bad plugs maybe?

 

x2 did you start it after you installed it and b4 you tuned it up

 

i switched the wires one at a time from the caps both times & doubled checked several times

 

ok it ran good you pulled it out changed all the parts you listed in first post installd and now runs bad correct?

 

fourthings you said you change that would affect running were plugs and wires,cps,cam sensor and new flex plate

 

the motor was put in with new plug,wires,& all the other things before it was started.

 

were the flex plates identical this regulates the cps signal

 

i went online & verified the right flex-plate with the box i have they also looked the same. im down to bad set of plugs or wires,map sensor & computer as the problem. thank you guys for the help,i really need to get my girl going

 

i dought the map sensor or ecm just happend to go out, when you installed the cam sensor you did not maybe bend the pulse ring