Continuing this thread; similar problem different P38:
Bad misfire on my '99 4.6 Bosch after complete top end rebuild (valve job, milled head, head gaskets, timing chain and sprockets etc...). Did all work myself and feared I made some boneheaded mistake. Which turned out to be the case.
In the unlikely chance someone else has such a misfire problem here are my symptoms and solution:
1) Checked all obvious stuff; spark wires tight etc. (Installed new plugs and wires during rebuild.)
2) Connected OBD code reader, showed following faults:
P0300 Random/multiple cylinder excess emissions detected Excess emissions detected on more than one cylinder
P0301 Cylinder 1 misfire detected Injector 1 excess emissions/catalyst damaging level of misfire
P0304 Cylinder 4 misfire detected Injector 4 excess emissions/catalyst damaging level of misfire
P0306 Cylinder 6 misfire detected Injector 6 excess emissions/catalyst damaging level of misfire
P0307 Cylinder 7 misfire detected Injector 7 excess emissions/catalyst damaging level of misfire
P1319 Misfire detected with low fuel level
(This last was no doubt due to initial start up with dry fuel line. In fact this fault was not present on next check.)
3) Cylinders 1,4,6,7? Seems weird I thought: 2 on each bank. Being a novice P38 _non-mechanic_ (and used to early Pleistocene mechanical distributor-with-rotor and single coil ignition) did not realize each side of coil packs ran 2 cylinders on each bank. Duhhh....
4) Was afraid I had mis-connected HT leads to coil packs. Found a diagram of proper ignition wire order on coil packs (see below).
Left pack fires 1,4,6,7 (my misfires) and right fires 2,3,5,8. Or looking at the packs as one unit, top row L to R: 1-6-5-8. Bottom row L to R: 7-4-3-2. Pain to get back to the coil but followed each lead; all tight and correctly in place.
5) Problem solved: found coil multiplug on left side off; probably bumped it loose when trying to bolt on the bracket that holds wiring harness to left rear head. Or just missed connecting it; nothing back there is easily visible. Reconnected and engine runs like new, no fault codes. More power, smooth as silk at 155k miles.
Amazing how much difference a fresh top end -- and correct ignition -- makes.
late 1999 P38a 4.6 Bosch North American Spec
previous Rovers: Series IIa 88 and 109, non-USA spec Defender 130
daily driver: 2008 Ural Gear-Up 750