Plugs and coils Day 2. List of tools, parts and photos at the end of this post.
Regarding the question about when to change plugs. The interval for changing plugs can be 100k miles according to Ford, but I would definitely not recommend that based on the condition of my plugs. They were definitely well worn and needed replacement (the van was not abused or run hard). The engine ran fine and idled smooth, but I am preparing for a 6 week trip to Alaska this summer and wanted to replace the coils and plugs as preventative maintenance. I wouldn't replace plugs before 50k miles. I would say 65k-75k miles is the sweet spot. I would lean toward 65k if your rig is run hard.
Finished up the job today. All in all, it was not too bad of a job. It's time consuming so if you have the time it's a worthwhile endeavor because you will get to know your engine. After getting everything prepped the night before (about 3 hours to strip everything down) I spent close to 7 hours removing the old coils and plugs and installing them. A big part of the job that is time consuming and part of why I wanted to do this job myself is that you need to clean out the plug holes. There are deep holes about 6" deep that the plugs go into and the boot goes on top of the plug. The boot is supposed to prevent debris and water falling down in the hole but all of the holes had debris, some much more so than others. A couple of the holes had evidence of water because a few of the plugs were fairly rusty on the outside (see pictures below). My method for was to vacuum the top of the engine with a brush attachment to remove as much of the surface dust and debris. The I used a blow gun with a compressor to thoroughly blow off sand, dust, small pebbles and dirt from all around the coils and fuel rail while everything was still in place. Now it’s ready to start replacing the coils and plugs.
I started on the passenger side as this looked like it would be the more challenging side which ended up being true. I spent 80% of the time doing the passenger side and the driver side went very quickly. I started with one that was easily accessible on the passenger side which is the plug closest to the rear of the van. I wanted to start with an easy one so I could understand exactly how the coil and plug removal and install process worked. I zip tied the thick wire harness up and out of the way by attaching it to the transmission dip stick tube that runs above. I put a zip tie at the front and rear of the engine and this was a huge help to access the coils and plugs. Next, I removed all of the wire connections to the coils and the injectors. You don't have to worry about mixing up which wire goes to which plug because the wire length is exact and you can't confuse a coil connector with an injector connector because they are a different shape and color. Now that all of the connectors and wire harness is out of the way you have better access. Not good access, but just better access. Without doing this I don't think you can get the job done.
To remove the first coil, you need to remove a small bolt that secures the coil in place. Once removed, you can pull the coil/rubber boot. It will literally pop off with a good tug. Next, I attached a bendable straw to my blow gun. It was a large plastic straw that has ribs that make it bendable without restricting air flow. Having 2 blog guns was handy. One with the straw attached and one without. I did this because there is not nearly as much power as with the blow gun with straw than the regular blow gun and I use the more powerful option as much as access allowed. I put the blow gun in the plug hole and blew out all the sand, dust, pebbles, etc. I did a thorough job of this making sure to blow off the engine then blow in the hole, blow off the engine blow out the hole as many times as it took to get all debris out of the hole and completely off the engine so it can't fall back in. Then I loosened the spark plug and backed it out a few turns and then re-blew out the plug hole. Loosening the plug a few turns will loosen up debris that is packed in the bottom of the hole. Every plug hole has more debris blow out after loosening the spark plug. Some were much worse that others and I had to loosen a little the blow out then loosen a little more then blow out until no more debris blows out. This probably sounds overkill but getting sand and dirt in your cylinder is not good and I doubt that a mechanic shop would do as good of a job as I did taking care not to get crap in the cylinder.
Once no more debris comes out, I removed the plug the rest of the way. Next is prep the new spark plug. I checked the gap (should be .054) first. Some were right on and some were gapped too big. I closed the gap by putting the plug in a vice and gently tapping to close the gap. Next, I put Permatex Anti-seize #80078 on the threads leaving the 4 threads closest to the electrode dry. I did quite a bit of research about anti-seize and despite spark plug manufacturers recommendations, I used it anyway. The consensus I found is that people were stripping out plugs because the anti-seize makes it easier to over torque and the plug manufacturers were being sued.
Now that the plug is ready, I inserted it into a magnetic 7/8" plug remover and extension with flexible joint and then inserted the plug and extension in the hole. I hand tightened the plug to make sure I didn't cross thread it and then torqued to 22 ft/lbs. This is 20% less than the recommended 24-28 ft/lbs. because I am using anti-seize. Once torqued, I blew out the hole one last time.
Now its time to prepare the boot. I put a dab of dielectric grease on the coil end and added some on the seal area of the boot to help keep out debris and water and also make it easier to push in the boot. Now that the boot is ready, push it in, twist and push, then twist and push some more to make sure you get it all the way down and connected to the spark plug. Then align the bolt hole and hand tighten the bolt that secures the boot to the engine. Again, I hand tighten to keep from cross threading.
The next 2 plugs I did were the hardest. After understanding how the process was going to work with the first easy one, I wanted to get the hardest plugs out of the way. Still working from inside the van on the passenger side, I removed the second, third and fourth coils. This gave a little better access to the third and fourth plugs which were the hardest. After going through the blow out process (see above) on all three plug holes I removed the fourth plug (counting from the back to the front of the engine, I'm not referencing cylinder numbers here for simplicity). To remove the fourth plug, I had to use the magnetic plug socket/extension, an 8" extension, a 6" extension, then a universal socket joint to make nearly an 90 degree bend and another 8" extension. This brought the end of the extensions to where the ratchet could connect all the way on the outside of the dash. This made loosening the plug actually easy. Without this set up, I can't imagine how you could get it out (and back in). There is so much crap in the way (vacuum hose, transmission dip stick tube wires, fuel rail, more wires, etc.) that access is impossible without an extension set up like this. Get yourself a set of 3 extensions 3", 6" and 8" that are 1/4 and 3/8 with adapters (6 total extensions) and get adaptors 3/8 to 1/4 and 1/4 to 3/8. This will give you lots of options for getting the correct length of extensions. I use all kinds of combinations and just about every cylinder was different. After going through the plug removal and insert of plug four, I moved on to the third plug which required a similar extension set up as the fourth plug. After inserting the third plug I went back and installed the coil/boot for plug three and four. Doing it this way just offered better access. Next was the second plug and this one had easy access. The fifth and final plug on the driver’s side was accessed from the front of the van under the hood. Again, a combination of extensions were required.
Once finished with the passenger side I put everything back together before moving on to the driver’s side. I triple checked that everything I moved, disconnected, etc. was put back together and in its rightful place. The battery is the only thing I didn’t install on the passenger side. This was the very last thing that went back in.
Now on to the driver’s side. This side went quickly. There is much better access, but I still zip tied the bundle of wires up and out of the way at both the front and back of the engine. All of these plugs had pretty good access. Still had to use different combinations of extensions but all when out and back in with relative ease. A couple of plug holes on this side were really dirty and I had to blow out repeatedly to get everything out and much more so than any others on the passenger side.
Here is a list of tools and parts for this job, some I had some I bought on Amazon.
-Magnetic swivel spark plug socket with 6” extension (this is a must): https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
-Universal Joints (another must): https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
-Permatex anti-seize #80078 (silver tube/bottle)
-Long flat head screwdriver 12” is helpful for getting off hard to reach clamps for the air intake and removing the plastic anchor plugs that hold the plastic coil cover to the wire harness on both sides.
Parts: I got both coils and plugs at Rock Auto. They had a good price and delivery was prompt and parts were genuine Motorcraft. I was reluctant to buy on Amazon or ebay based research.
Motorcraft coils: DG508
Motorcraft plugs: SP479
Photos of old spark plugs with 87k miles. The electrodes were very eroded and the was build up on the metal arm. https://photos.app.goo.gl/TdbHfNwFB4as9aRV7
General photos: https://photos.app.goo.gl/JiHqGSYbBFoESvmNA