i have a 2006 ford f150 xlt v8 5.4 150,000kms. when im driving and the spedometer reaches 70mph the truck starts to buck and jump until i reach a speed over 80mph this happens when i am slowly accelerating, if i push the gas harder it doesnt happen anyone have any ideas as to what would be causin this? any suggestions would be greatly appreciated..thanks

 

Can you get it to do it at the same RPM in a lower gear?

 

sorry for the post but it is suppose to be between 70 and 80 kilometers per hour

 

May have a little water in your tank. I'd first try putting Heet or Sea Foam in the tank to see if it helps.

 

tried it it didnt work any other suggestions?

 

brought the truck to ford dealership got the plugs changed and now works fine

 

Good to hear.