L322 Missfire after spark plug change - How hard can it be!!!

Hi all,
2003 Range Rover L322 4.4L Vogue LPG/Petrol

I have just changed the spark plugs on my RR L322. Now I have a misfire and the engine symbol comes on intermittently whilst driving. Misfire can be slight or major juddering of the car. Car ran perfectly before the spark plug change.

The spark plugs are the same as the ones removed but new! I simply removed the access cover. Undid the coil nuts and removed the coils to one side. Removed spark plugs. Gave everything a wipe over with a clean rag. Fitted new spark plugs. Refitted the coils and refitted the cover.

On the test drive the misfire and engine light occurred.

I decided to carry out the change again. I did exactly the same thing again only removed and refitted the new spark plugs.

I also made sure this time that I firmly seated the spark plug to coil rubber extension connection.

On the second test drive the misfire and engine light occurred again.

Is there anything I am obviously missing?

Thanks in advance for your help.

Bison :boom:

Cheap/****/duff plug? I only ever use NGK - quite simply the best plugs.

Spark plugs not gapped correctly or the electrode has fallen down and touching the tip, loose connection broken coil pack internally the list is endless cheapest and easier thing is to remove the plugs check the gap and the electrode tip, if the misfire occurs at idle you could disconnect each coil separately to see if the engine noise changes (if they are single coils) when the engine noise and running state doesnt change you have narrowed it down to that cyclinder and the checks continue or to stop all the faffing around get it on diagnostics to find out which cyclinder it is.

Thanks for your prompt reply guys,

Stuckagainsteve - Brand new set of NGK Laser Platinum BKR6EQUP fitted.

Matt1987 - Not sure you can adjust the gap on these plugs. Misfire unfortunately doesn't occur at idle. I will check gaps just in case I have nocked one on fitting.

I am beginning to wonder whether I have a dodgy plug.

I posted the question just in case I was doing something stupidly wrong!

Thanks again,

Bison

Unlikely to be new plugs,

I had a misfire recently and it turned out, after a whole lot of faffing and me not being smart enough, it was a dodgy coil connector....probably caused by unplugging and pulling on the rubber boots/wires instead of the rigid connector.

it happened after a plug change so this only entails disturbing coil connections and the little earth on Number 2 coil, if you could isolate the problem cylinder by unclipping coils one by one when running, all the better. Change round coils to see if fault remains on that cylinder, if it does its more than likely a connector issue, remove rubber boot from back off connector to see if a wire is loose... wiggle it, or in my case i think they had special tool that removes the wires from connector block, in my case they did this and re-crimped, just use vice grips if you can get them out. Also clean the earth connection on Number 2 with fine sandpaper and grease up.