FStorm150

So at 90K miles, I had the plugs replaced on my 05 5.4. I knew it was time to do so, as they were most likely original plugs and the dreaded recommended plug change was looming. At the time I was experiencing the bogged down, shutter feeling when the truck was in overdrive at around 1200 rpm's. Had the plugs changed out (after a hefty bill due to half of them breaking off), used the suggested Motorcraft SP515's and all was well. The shuttering went away and I had restored power. Now a little over 30K miles later at 121K miles, the same thing was happening again. Bogged down, bucking like a bronco when trying to shift out of overdrive. Since the plugs were just replaced 30K miles ago, I figured there was no way they could have gone bad already. I started fearing the worst, thinking it was something like a coil pack, injectors, fuel pump, etc. Took it to Ford for them to scan, couldn't come up with anything. Only advice they could give me was that maybe plugs went bad early due to me using a programmer, and "sometimes programmers overwork the spark plugs and cause them to fail early". I brought it home from Ford thinking they were idiots for blaming it on the programmer, and decided to start guessing what it could be. I figured the cheapest fix to try first was to replace the plugs again as well as the boots. Bought the parts myself, took it to my local mechanic, and presto - all is well again. None of them broke off this time, all came out fine. No more loss of power or shuttering and she runs fine again. I'm still shocked that those plugs went bad after 30K miles, but maybe this is common? Perhaps my truck just eats spark plugs? Does anyone here believe there is any truth to what the Ford tech told me, in that a programmer can overwork the plugs and cause them to fail early?

lewissa81

I'm not sure if the tuner itself would, but I can see some conditions to warrant the use of one to stress the plugs more. Modifications can stress the engine, and cause a person to run it harder. A tuner will compensate to a degree, but not necessarily completely.
I'm not sure what mods you have, or that applies to your case though. Just my thoughts.

jamie930

Were the COP boots and springs changed the first time around?

I had the exact same issue till I change the COP boots and springs