I have a 2007 F150 King Ranch that now has 150,000 miles on it but has had regular maintenance performed prior to the maintenance schedule Ford suggests. For example, I had the original garbage plugs replaced at 60,000 not the suggested 100,000. The plugs were changed at a reputable shop with Motorcraft Platinums. I got a misfire at 110,000 and could hear a "ticking" noise when close to the truck. I once again had the shop go through the plugs and replace whatever was necessary. They discovered two of the plugs no longer had electrodes on them so all of the plugs were replaced again with the only ones recommended, namely Motorcraft Platinum. Fast forward to 152,000 and it started to run rough sporadically and then finally threw a code. The analyzer indicated the problem was on cylinder #4 so we changed the coil as the first attempt. It fixed the problem for about three blocks and then came back. This time however, it seemed worse. With the analyzer connected it was indicating problems with Cylinders #4 and #5. Replaced the coil on #5 and again it ran better but still had a problem with #4. Took it into the shop today where they pulled both plugs and found #5 to be looking pretty normal although it was performing well in the truck. #4 however had not electrode on it at all. Completely gone! Both plugs were replaced and the truck is now running fine again and the "ticking" noise, which I think was a spark clash is also gone.

Anyone have any ideas or words of wisdom here on what could be causing this? I like my mechanic an stumped. I especially don't appreciate the fact that it looks like there is only one brand of plug recommended for this engine.

 

What was the condition of the other plugs when removed?
Are you using any kind of fuel additive?
Not knowing what kind of driving you do, but a lot of so-called special plugs don't always live up to the hype.
Another line of hype, plugs performing like new after 100,000 mi. The more you learn the more frequently you will have the plugs replaced The engine may run with not much lowering of performance noticed,,,,because it is so gradual, , but new plugs will almost always provide better performance.
If it is of any help, the manufacturers pay people a lot of money to test and determine the best average performance with various parts and that is how they determine what parts perform best on average for the vehicle. There are parts manufacturers that do improve some aftermarket parts, most of the time we get pretty good results with OEM recommended parts.

 

Hi Hanky, thanks for your response. To answer your questions, we do not use any additives in our fuel. The other plugs were intact with the normal wear that you would expect from a plug with 20,000 miles on it. I do normal on road driving between local runs and highway. The plugs we are using are OEM Motorcraft Platinums SP546 which is one of two or three recommended for that 5.4 Triton 3V. The others built for that truck are Champions and some other brand I don't recognize. These are not "special" plugs.

In checking the history at the shop I did discover that the plugs were replaced at 133,000 and the truck now has 152,000 on it so roughly about 20,000 miles to failure. If these were specialty plugs, that would be my first suspicion, but they are not. Since the tip was completely gone and I don't know where it went, I had them do compression on that cylinder to make sure it was ok and it did check out, so I am a bit baffled.

These plugs are factory gapped at .045 and the contact on the bottom of the plug is not an "L" shape, rather a continuous loop from side to side on the plug so you do not have the option of gapping this plug.