So I just had my plugs replaced two weeks ago thinking I was finally past any engine troubles and yesterday while merging onto the highway things got hairy. Before my spark plug change I would have a little misfire but nothing serious. Since the plug change while merging it felt like all 8 plugs were missing, the trucks power faded and my speed dropped to about 40mph. I nursed it to the top of the hill and took it easy and the truck went back to normal. Since then I've been very timid when accelerating hard. What could this be?

 

How many miles ? Possible COPs need to be changed if a lot of miles

 

When you(or by the sounds of it whoever) did the plugs pull the negative battery terminal off? if not pull it off over night tonight, put it back on in the morning and do a TB relearn. Then see what it does.

 

Truck is a 2005 with 98700 miles. I'll unhook the battery tonight (negative side)and see how that goes.

It was just so odd, my misfires previously we so minor. This was borderline violent.

 

Exactly like my issue before I changed out my plugs and cops, has not happened since I changed them.

 

Did you use Motorcraft plugs? I put a set of Champions in once and they did that constantly. Yanked them out for another set of Motorcraft and never had an issue again.

 

before you pull battery cable, run a computer test, even if light isn't on. it might have a code. I have seen it many times, somehow disturbing by tuning them up always seems to bring bad cops to the surface.

 

So I unhooked the battery for the night and thought that may have fixed the issue. But today while merging onto the highway the truck started to sputter and jerk. The harder I pushed the gas the more the truck would shake. Again I nursed it tot he top of the hill and drove conservatively for a while and the issue seemed to go away. I noticed that all these things happen within the first ten minutes of my drive but as the truck warms up the shaking stops, the engine runs smoother and things go back to normal. What the heck is up with that?

 

Sounds like more of the COPS. Sounds like the best way to go about fixing it is just getting some Accell ones and redo. After putting the new ones on, do another relearn and hopefully that should fix your issue.

 

I was dreading that. How much does that repair run? I'm taking it in tomorrow to see what the mechanic says.