Flashing check engine light Discovery 3S 4.0 V6

I have the EXACT same issue on my LR3 (yes I'm in USA but the 4.0 v6 versions here are almost non existent so I found this post from a Google search). My car is giving me misfires mostly on one cylinder at idle (although sometimes another cylinder on that bank), and car is negatively trimming that bank also. I have literally checked everything, compression, leak down test, fuel pressure test, replaced injectors, replaced plugs, checked for vacuum leaks. Even taken off valve covers and made sure timing is correct. I can not figure out the issue. Now I am thinking maybe O2 sensor on that bank, or maybe the engine control module? Unplugging O2 sensor does not seem to have any effect however. Any information on how you (hopefully) rectified your problem would be greatly appreciated, thank you.

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Originally Posted by Cconra14

I have the EXACT same issue on my LR3 (yes I'm in USA but the 4.0 v6 versions here are almost non existent so I found this post from a Google search). My car is giving me misfires mostly on one cylinder at idle (although sometimes another cylinder on that bank), and car is negatively trimming that bank also. I have literally checked everything, compression, leak down test, fuel pressure test, replaced injectors, replaced plugs, checked for vacuum leaks. Even taken off valve covers and made sure timing is correct. I can not figure out the issue. Now I am thinking maybe O2 sensor on that bank, or maybe the engine control module? Unplugging O2 sensor does not seem to have any effect however. Any information on how you (hopefully) rectified your problem would be greatly appreciated, thank you.

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You need the DTC codes otherwise anything else is a guess.

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Originally Posted by loanrangie

You need the DTC codes otherwise anything else is a guess.

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Codes are always the same no matter what I do, p0304 (sometimes p0306) p0300, p0316, and sometimes p0405, although thats and egr code and doesn't seem to always show up. Moving around coils, moving plugs, changing plugs, etc have all resulted in exact same performance. Oddly enough I drove the car this morning, fuel trim on the bank with the misfire was a little less negative, but still a misfire persisted. I am losing it over here trying to track this down.

I had a similar problem with my 4.0 litre V6 which I eventually traced to a bad connection on the crankshaft position sensor (I think that is what is is called) which is situated at approx 11:00 position at rear of engine on the bell housing when viewed from inside the vehicle looking forward. Mine was a corroded connection, a clean up and all was good. It was not the easiest to get too. Any rattles from the engine like a timing chain noise as this can also cause a misfire.