5.4L 2WD XLT 225k miles. The vehicle will go from proper resistance to overly sensitive in an instant. It never used to do this. It is incredibly dangerous on the highway. I have experienced this around town as well. The problem started with no warning and seems to be delayed on much colder days(45F and below) until everything has time to warm up, maybe 5+ minutes. My Drive to work is 15 minutes and it happens before I arrive. Power steering pump makes no noise. Vehicle has been aligned, replaced all steering ball joints, bushings, control arms, and sway bar bushings. Only thing I haven't replaced to my knowledge with the steering is the steering fluid and gear box. I plan on doing a full flush of the fluid today and going from there. Any other ideas or suggestions?

 

Do you trust the shop that checked out the front end and did the alignment? A couple years back after I got an alignment and my Navigator was all over the road. I brought it back and the person that did the alignment told me he couldn't get one of the tie rod adjustment bars to turn so he tried to compensate with other adjustments. Needless to say I brought it somewhere else that did it correctly and the truck drove straight and true after that.

 

You didn't say if your truck has air suspension or not.

I'm *guessing* that it has an EVO (Electronic Variable Orifice) power steering pump which varies the assist based on vehicle speed.

I,d get it scanned for any pending codes.
You may have an issue with the VSS which is used to control the EVO.

If you have air suspension, the SAS (Steering Angle Sensor) up under the dash also has an effect on the EVO. Did this issue come up before or after your wheel alignment?

 

Had the issue before the alignment and it doesn't feel like the alignment is the problem. It went from being an intermittent issue to a constant problem once the vehicle warms up.

 

Do you have the air suspension or not? The diagnostic is different for each configuration.

The following is an excerpt from the service manual and is the preface to the diagnostic routines section.

 

No I do not have the air suspension.

 

Do you have a scan tool that can read the EVO control module?

 

I have an OBD2 code reader for the truck, is that the one? I'm also researching incase this is the issue.