Schreck425

I have a 2001 4.6 F-150 Lariat. It was running fine. While driving it started to run hard, vibrating pretty hard. Even does it at idle. The only time it doesn't do it is when I am slowing down. Autozone checked the engine code and it said most likely fix is to replace the thermostat. I wasn't fully sold on that but wasn't sure what to do so I took it to a shop around here and they did their own diagnostics and said they replaced the thermostat and all is well. Problem is, the vibration still comes back occasionally. It definitely improved things because when I drove it to the shop it was vibrating very consistently and I couldn't get above 45 mph. Now it runs fine most of the time but when I come up on a hill it starts to vibrate again, just not nearly as bad...

I don't know if I should take it back to them or what.

Anyone ever seen this?

fordguy2100

1 what started vibrating? Truck or engine?
2 what was the engine code? Without it we can't give an educated answer
3 I've never heard of a thermostat causing trucks or engines to vibrate???
Yeah definitely need the code that was thrown

white89gt

Agreed.... it might feel like you've got a loss of power because the programming is off, but vibration is usually indicative of an engine misfire, something out of balance, etc.

Specific codes are needed here.