There are many, many threads on this forum about replacing the plug wires. I recommend you read several of them before getting started.

If you are replacing the wires you may as well replace the spark plugs at the same time. There are a lot of opinions on the forums about what plugs are "best" for the DII. The original equipment plugs for the 4.6 are Champion RN11 YCC. Use them. Don't overcomplicate the situation. You'll have plenty of other challenges to think about.

Replacing the wires is an easy job made much, much more difficult than it should be due to the location of the coils at the back of the engine. Here are a couple of highlights.

• Your truck is a 2003, which means it likely has secondary air injection (SAI). That means it will be much, much more difficult to replace the wires without removing the upper intake (plenum) due to the SAI pipe that runs across the cowl restricting access.
• If you have very small hands (like me) you may be able to still do the job without removing the upper intake. I did so, but my truck doesn't have SAI.
• If you remove the upper intake you'll need a new gasket to reinstall it.
• In either case I found it easiest to lie flat, stomach down, on top of the engine. I used a closed-cell foam camping sleeping pad to lie on but an old quilt or blanket could work too.
• Whether or not you remove the upper intake you'll need to remove the brake servo vacuum line from the intake. I didn't and broke the line. It's a counter-intuitive connection: press in on the red plastic ring while pulling out on the line itself.
• The same goes for the breather connection next to the brake servo vac line. Remove the hose from it and then unscrew it from the intake. While you're at it, or if you break it, you can replace it with a brass version from the plumbing section of Lowe's or The Home Depot for about $5. Use Teflon tape on the threads when it's reinstalled.

 

Did the wires today, many thanks to all the advice here on the forum. I do have the secondary air injection and I had to remove the pipe or it would be have been pretty much impossible. Idles smooth now and doesn't buck under a load. Of course I found more things wrong while under the hood! Good thing I have a spare vehicle while I work on the Rover.

 

Better check under your vehicle and see if it's a serviceable shaft. For $900, I bet it was genuine. that means you have roughly 90-100k life from the time it was installed to when you'd need to replace it.

I wouldn't panic and replace it now, it will be perfectly fine.....for awhile.

A reputably built serviceable shaft can be had for $350.