This concerns a 2008 4.2 Supercharged Range Rover Full Size; however, it's the same engine in the X308 R and there is likely greater knowledge and experience on this forum on this engine.

Two days ago, the vehicle was stumbling and misfiring; however, the check engine light never went off. I have a Autel Maxisys 906 and the only codes recorded were numerous misfires in cylinder 7.

I installed a new Delphi coil and spark plug. The engine immediately smoothed out. However, once I turned the engine off and back on again, I would get a check engine light and a code P0351. On reset and restart no check engine light would come on while driving; however it would come on again after the engine was turned off and on again. With the Maxisys connected, I could see the code even though the check engine light didn't trigger on. The code comes on and the engine is running smooth; the fuel injector pulses are consistent on all cylinders; there were no misfires; the fuel trim is within spec; etc. but the code keeps occurring.

Here's what I've done:
1) Took the brand new ignition coil and spark plug and swapped it out to a different cylinder bank. This did not remedy the situation.
2) Visually inspected the wiring. Did not see any breaks.
3) Use contact cleaner on the connector.
4) Compared ohm readings on the 4 pin connector on cylinder 7 as compared to cylinder 5 connector. All reading were the same. I did this with the vehicle off and in key position 2.
5) Compared voltage on the 4 pin connector on cylinder 7 as compared to cylinder 5 connector. All reading were the same. I did this with the vehicle off and in key position 2.
6) Jiggled the wiring harness.
7) Disconnected the wiring harness connector to the computer and reconnected.
8) Disconnected the battery for 30 minutes and reconnected.

Any advice would be appreciated.

 

it might be the ignition coil itself i tried delphi maf sensor which is supposed to work on my jaguar but didn't work at all . get NGK or Denso . Also Check the ignition control module .
Also it might be bad injector on that cylinder.

 

Problem solved. Apparently the ignition coil on cylinder 1 failed at the same time I replaced the coil on cylinder 7. I just assumed it was cylinder 7 because it occurred immediately after the fix. Figured this out while writing the post that P0351 is the code for ignition coil A, which is for cylinder 1. Date code on the both Delphi coils were from 2017, which I installed in Feb 2018.

 

They are reputed to fail together for some reason. I've had this problem.
Just remember to have a few at hand and not to try to drive it like that due to the unburnt fuel going into the catalytic converter.

 

Yes, I just didn't expect a "name brand" coil would fail in 20 months and less than 5K miles.
However, that's my experience as well, when one coil goes, the others will generally fail soon. I had the same experience on both my DB7 and DB9, which is a major chore to replace on my own.