I have a 05 F150 KR and it shudders at 50 mph but only when on the freeway or going up a slight incline! Any ideas on what could be causing this? The shudder seems to be rotational, as though something is spinning and causing the shudder.

 

How many miles are on your truck? Do you do any off-roading? Does it feel like the driveline or the engine? Is the CEL on?

 

It has 98,000 miles. No off-roading, only highway and city miles. It feels rotational, so i think its something with the engine? And the CEL is not on. I recently had all the fluids changed, fuel filter replaced, the whole nine yards.

 

One of your coil packs has probably gone bad. I had one go bad and only at a certain rpm when accelerating from low speed it started to shudder

 

It doesn't sound like it's driveline related. As 02KR mentioned, it could be weak spark from one of the coils, but it seems relatively early for one of them to fail. It's hard to diagnose these symptoms if it's no yet throwing a code. It would be best to hook up the truck to an OBD II reader and look at engine data such as fuel trim, O2 sensor function etc... while driving under conditions that exhibit the symptoms you describe.

In any case, you could unplug and reattach all the connections to your injectors and plugs just to make sure they're all tight and to remove any corrosion on the connectors themselves. Also consider pulling the boots off the plugs to make sure there's no corrosion on either end of the spring inside the boot.

Will it stutter if you stomp on the accelerator at that speed and going up hill? I think the computer likes to modulate EGR flow at around that speed with low throttle openings. At close to fully open throttle positions, the computer closes the EGR valve. On these trucks, there's no separate DPFE sensor so if cleaning the carbon out the EGR valve and lines doesn't help, you may have to replace the whole assembly.

 

Mine went out at 85,000 and my moms 5.4 expedition went out at 105,000

 

I have the 4.6, but the coils are the same. 190K and all are original. If you measure the resistance -- should be around 13 ohms when cold and drop down to 1 ohm at operating temp., then it's probably just corrosion at either end of the spring, assuming the spark plug well is dry and the boots are in good shape.

I've had a few misfire codes along the way and this has always fixed it for me. In general, I think failures are pretty rare for these solid state electronics.

But our OP doesn't have any codes so who knows but if he's so inclined, replacing plugs and this check would be a good place to start.

 

If I had to find a short way to describe the problems with our truck, this would be EXACTLY the thing. We have an 03 F150 XL and after having all the fluids changed as well as fuel filter it started this crap (it was about 7 days later though). After some checking, the alternator was gone. (I don't put many miles on it right now so I guess we just hadn't experienced any issues yet). After changing out alternator, problem is better but not gone. Found out that freon from hose was leaking onto alternator and killed it. (Had been over filled).

Now, we still don't know what's going on. This truck has been flawless, with the exception of the battery dying two years ago and a problem with the ac. I am sick. We are not mechanic types, though necessity is certainly trying to make us so and we are actually enjoying it. I'd really really really love to hear any ideas y'all might have. We bought one of the obd II thingies and are planning on using it tonight to see what codes it throws. Ideas?