Levi Lundgren

Have a 1996 XJ 4.0 with a persistent misfire. I have done piston rings and head gasket but still cylinders 1-3 are completely dead despite good spark and known good fuel injectors. Did compression tests on 1-3 and their readings were all below 60psi, 4-6 were acceptable. 1-3 perform exceptionally well on cylinder leakdown tests surprisingly. Unplugging fuel injectors for 1-3 does not change the way the engine runs (even all at once) but unplugging 4, 5, or 6 makes the engine die. This has had me stumped for an embarrassing amount of time, any advice appreciated.

awg

using logic,

if you have spark, fuel and air verified, and the relevant cylinders dont leak, but have inadequate compression;

that would suggest valve train actuation is somehow improper, have you checked relevant clearances of pushrods, cam etc ?

I would certainly hook up a mechanical vacuum gauge, a very cheap tool but will give you some clues

Do you have any OBD2 codes ?

lawsoncl

Wiped cam? When you had the head off, did you pull the lifters out and look at the cam lobes?