Hi all, running the 5.0 SC motor, we've just done the timing chain, guides, tensioners, did not do the cam phasers though, and got the head rebuilt on the passenger side (Australia), after putting it all back together we were getting random misfire 5 & 6,
New spark plugs, Coilpacks, Injectors - same thing.
Disabled the aux belt so the supercharger out of the equation, and isn't throwing the knock sensors off and perhaps causing misfire - same thing. I am getting a slight knock in the SC, its bearings have 130,000kms on them. Couplers been replaced though in the snout.
Swapped cyl 1 & 2 plugs, coils + injectors into 5 & 6 using re-seal kits each time - same issue.

For some reason, the ECU is not firing 5 and 6. If we detach the loom clips for the injectors 5 & 6 we also get "injector circuit break" as well as "Random misfire". If we plug the loom clips back in, all we get is "random misfire", so this tells me the ECU is pulsing injectors in cyl 5 & 6 and its spraying fuel, just no spark.

Any idea's ?

I've ruled out;

• the SC knocking (coupler has been replaced),
• faulty cat or O2's, since its not the entire bank, just 2 cyl's
• knock sensor
• compression test was 120 + all cylinders so its not that
• timing was aligned using appropriate cam locks, timing tool, etc, and done by an ex Jag mechanic so its not timing related.
• head was rebuilt on that side by professionals, all new valves and seats, basically a brand new head.
• brand new genuine gaskets everywhere from Jag/LR.

Next items to test with dad; is continuity on the 3 wire plug on the coil pack, and 2 wire plug on the injector, for cyl 5 & 6,
check ground and signal wire, try our best to trace it all back to the ECU. We may have damaged a wire or some wires in the loom after bending them back during the timing chains, since the loom hasn't moved for 130,000kms (8 years), its been stale in that position so we could have MAYBE caused damage ?

any ideas logical or hail-mary, would be appreciated.

 

You're in the post 2015 X260 forum here. There's a forum for the X250 on this site where you may get more answers. Hope you get it sorted.