I seem to lose the number 4 and 6 injector when the engine downshifts going uphill, firing one second then nothing. It seems to be 4 and 6 as when the miss is happening, unplugging these injectors causes no difference to the rough idle. As soon as I turn the engine off and then fire it back up, they seem to be firing. This assumption by unplugging the injector and noticing a difference in the idle. It is a 2000 XJ 4.0. I upgraded to 12-hole injectors and seemed to have gotten rid of a constant miss it had with the stock injectors. Has anyone heard of this before? Is it most likely something in the PCM cutting out the injector pulse, or the coil packs cutting fire for some reason under the right conditions?

 

Check the wiring harness for damage, especially where it goes from the engine to the firewall.