97 4.6 4X4 135k

Shudders at 40 MPH round 1200 RPMS while in OD.

Bad coil pack? Bad torque converter?

No codes other than P0155 Bank 2 sensor 1 O2 heater circuit.

Any Ideas?

 

shudders during the shift or just at 40mph?

 

just at 40, if I go slower it stops, if I go faster it stops.

 

it's not a bad coil pack because you would be throwing a misfiring code if it was

 

sometimes the engine light wont come on, go to autozone or advanced and get your codes pulled.

 

Could be imbalanced tires or bad idler arm.

 

Well I just had the tires rebalanced about 2 months ago and rotated. Theres no shaking in the steering wheel, just a shuddering from the whole truck. Feels almost like it's missing or having flat spots in all of the tires. It's only when I hit 40 though, freeway it drives fine without a hitch.

 

its coil packs, our year and model has been known to get water in rear cylinders, that shudder is actually a missfire and is throwing un-burned fuel into your cats and gumming them up, happened to me. do a search of the site and youll see it is a common topic

 

https://www.f150forum.com/f6/1997-f-...-50-mph-43383/

https://www.f150forum.com/f6/really-...-26562/index2/

merry xmas, did some searching for you

 

That happened with my 2004 expedition that i used to have and it was missing at all speeds. I wonder why it's only doing it at 40 mph for him.