I have a 2000 ford f 150 with 180,000 miles. never had a problem runs great all of a sudden service engine light came on going up hill on the freeway front end seemed very shakey and power went flat.. put it on a computer and said cylinder 8 misfire anyone ever had this problem and can you help?

 

Try some new spark plugs and run some Sea Foam in your tank to clean the injectors. If you still get the error, you may need to replace the coil pack for that position.

 

Had this problem with my 2001, but it was number six that blew out. Change the plug and the coil and you should be alright, the shaking has to do with the loss of power in the engine. Because the #8 cylinder isnt firing, it jolts the driveline when it hits that cylinder as there is no power in that cylinder, so when it goes back to the other 7 it has all that power, and makes it feel like it shakes.

Hope this helps!!

 

I've been chasing that code myself on my 98 f150 4.6 I changed plugs wires coil and fuel injectors and the code was still showing. Finally I did Compression Test and the cylinder failed horribly.

I'd try a compression test along with the other ideas mentioned above.

Good Luck