I started using mid grade gas and then started having problems! My engine light came on with a P0307 Cylinder 7 Misfire Detected code. I switched back to premium and out in Lucas Upper Cylinder Lubricant/Cleaner. Problem seem to go away after resetting the engine light. Problem started again a few weeks later (same code) replaced all spark plugs and reset engine light. 2 months later same problem - P0307 Cylinder 7 Misfire Detected. Any advice appreciated!

 

You need plugs wires.

 

Thank you for your reply. Is this something my husband can do. Do we need to get the plug wires for all 8 and do we get these from the dealership?

 

Before you jump the gun, how many miles on the truck, when was it last tuned and were the plug wires replaced?
The gas did not cause the misfire, and as Spike has mentioned you MAY need plug wires.
How mechanical is your husband?
If you buy wires, order a set of 8 mm Magnacor wires from Cerrones, 650-365-4145, do not order the intake manifold gasket.

 

Yes you need to replace all 8 plug wires. You can use Land Rover wires but the Magnecor wires are better because they have a lifetime warrenty.
Whithout knowing if you have a DI or a DII I cannot tell you if your husband can do the work or not.

 

It's a DII 143000 miles, had a tune up @8 months ago and wires were not replaced.

 

You need new plugs and wires. The plugs that are in it are now fouled and need to be replaced. The bad plug wires are whats causing the mis fire.
How mechanical is your husband? It is about a 5 hour DIY job. He needs to remove the intake plenum and if the truck has ACE and/or secondary air it can make the job harder yet.
It can be done without removing the intake plenum but you need really small hands and the paitence of a kindergarden teacher.

 

I did it in 1.5 hours with average size hands. Just remove the secondary air tube running across the rear of the motor right over the coil packs. I used a long flat tip screwdriver to pry the old ones off. There are many threads on this site with pictures and directions on how to do it. Just search...

Cheers,

Pete