Hi there. Got an issue with a q7 3l 2014
Steering is hard and stiff,sometimes,very rarely is actually nice and easy
Have changed a new pump,new refurbished rack, have test the wire between the sensor on the rack and the module and it has connection.
Any ideas please?

 

Little confusing when you start a new thread on same issue you prior posted about...bit like reinventing the wheel, except we lose all context from original thread, etc.

The last comment on original thread is suggesting you check the condition of the steering shafts U-joint to see if it is corroded, and may require lubrication or replacement if it is really bound up, etc. You didn't respond to that, so it's a good place to start as that is a mechanical pinch point if that joint is seized up.

You've changed the super expensive parts (hydraulic pump/steering rack) out with no result/change apparent.

Two things that often cause myriad issues on the Q7 is the wheel speed sensors (ABS sensors), and also the presence of vacuum leaks from cracked connections/old hoses/brittle plastic, etc., which impacts a lot more than you realize on this car.

The ABS 'rings' that those wheel-speed sensors read off of are attached and integral to the wheel hub on a Q7 (not repairable item...swap for new hub), and sometimes they get damaged, which then prevents getting a steady reading, etc., so there's some things you can easily check, both mechanical and non-mechanical in nature. Not sure which control module is involved with the power steering, but that'd sure be on my radar too.

On the German cars I've studied with similar 'hard-steering' issues, the culprit is often the speed sensor linked to the power steering feedback loop that is the problem, as relates to either a wiring break/damage or problem with that sensor's feedback sent, etc.

How does your brake pedal feel, I wonder? Is it low? If it feels spongy, there's a very good chance you've got a vacuum leak at the brake booster's vacuum hose connection where it meets the engine's vacuum hose (a common, brittle plastic failure point); these two lines connect just inside the engine bay right next to the firewall, etc.

 

It cannot be related to abs sensor as any imperfections will trow a light on dash.
Vacuum has nothing to do with steering system
U joints have been all treated
And regarding the speed sensor,have changed one underneath the front right wheel arch.
Brakes all good

 

When the work was done on the pump and rack, were the hydraulic hoses replaced?

This anecdote is very much on an unrelated vehicle (1976 F250), but I had extremely stiff steering on it for many years. I assumed it was the hydraulic assist (equivalent to the rack on the Q7), but I could not find a replacement, so I just let it go. Someone mentioned to me that it could be the result of an internal hose failure, so I figured I might as well give it a shot since the hoses were all original. I pulled them, had a local business build me new ones to match, and all my stiff steering issues were GONE. The rest of the system worked perfectly!

 

Hoses gone bad can certainly be a problem, but you don't normally see that unless the vehicle is pretty ancient w/original hoses, etc...which 1976 era F250 I'd call that ancient (and sturdy too).

Here's an Audi Tech document discussing the power steering types used in Audi vehicles, including a breakout photo showing there's an input shaft 'torque' sensor located on the steering shaft, etc. Yes, yet another sensor responsible for telling the steering system what you want it to do. You can also look up the full diagram/schematic for your specific power steering system in order to identify any bits you may not have looked at that have controlling interest in the feedback loop that makes it work:

https://www.audi-technology-portal.d...power-steering