Driving down I-95 at a respectable 75-80mph and the truck is running smoothly. Until I have to pass some knucklehead in a Kia. When I put the pedal down the truck accelerates, but poorly and VERY rough. Back off the throttle and everything seems fine. Only happens when I drop the hammer. Two hours of driving later, I get a CEL. “Back in the day”, you’d put Amoco white gas in it and blow out all the crap on the old airport road. Nowadays, with all the electronic wizardry? Anybody got any ideas??

 

How many miles on your spark plugs?

 

What codes are you getting? Without those, all anyone can do is make a wild guess.

 

engine and year would help as well

 

Code says #4 coil is misfiring. Which really stinks because I just replaced all the coils and plugs 5 months ago. How common is a bad coil?

 

Did you use OEM coils, or aftermarket replacements? Bad coils do happen, and generally show themselves at max load/cylinder pressure (aka peak torque).

We need engine and year to help you further.

 

What is the code?
304 or 354. Makes a difference.
Is the coil connector firmly plugged up?
Coils are like any other part, can be faulty out of the box or fail at any time.
.
The misfire under the conditions you describe could be water condensation in the Turbo Cooler being picked up by the large increase in air-flow.
Good luck.

 

Perfect. Move #4 coil to another cylinder as a direct swap, and clear the codes. If the code changes to the recipient cylinder then you have diagnoed it.

 

yes, I just did this with the truck of a friend and found a faulty coil. Replacing all coils it is like replacing all tires because you think one have a hole. First identify which one. And you need to replace that only coil with a new one. Instead of buying 8 cheap coils you can buy an oem one to replace only the identified as bad. And then you will find if the problem is the coil.

 

New does not mean good.