Well, my 2001 Excursion was having the same symptoms - abruptly jerking to the left, and when you try to correct it, abruptly jerking to the right and back and forth. It was worse when cold, and would lessen as it got warmer. Finally, last night, it got soooo bad, that one would have thought I was drunk as I couldn't keep it in a going in a straight line even at 5mph!!! Steering would jerk to the extreme left and then to the extreme right as if someone was physically grabbing the wheels and yanking them.

I was able to nurse it to my mechanic, who upon inspecting it, told me that the steering gearbox had grenaded internally (ok, not quite that dramatic, but the ghost had been given up). Alas, $700 later: new gearbox, PS pump, PS hoses and steering stabilizer and all is well.

 

Mine quit doing it after the new ps pump, but I oiled the u-joints at the same time so I am leaning towards bad u-joints now.

 

Same here. New pump and ATF and it went away.

 

I replaced U-joints only, been 8 months now and I have had no issues

 

Thank God I'm not insane.

I've been having this exact issue - intermittent jerking of the steering wheel (and of course the vehicle) from left to right. It is as if the steering cannot rest on-center. It jerks left, I try to pull it back to center, it reaches center, but then jerks right... I try to pull it back to center, it reaches center, but then jerks left...

I end up driving almost in a "letter S" taking up 1 1/2 lanes of traffic weaving back and forth.

Then eventually - inexplicably - it stops doing it, and drives fine, sometimes for days.

I am NOT a mechanic, so I've had it in the shop twice to a trusted mechanic, who was simply unable to diagnose, and made the best suggestions he could.

First time in, they test-drove, noticed "loose" steering, but not the severe jerking I described. So, he replaced the steering stablizer and the stearing gear box, thinking those were the likely culprits. I drove it away, and about 5 days later, it did it again.

Next time in, he was very perplexed, and felt very bad that he couldn't diagnose. He looked at all four tires, brakes, rotors.... noticed a rear caliper was sticking. He said that wasn't likely the problem, but it needed fixing anyway. He also did something with the ball joints that I'm unsure of - something about adjusting to a modified torque spec he read about.

He test drove, and it was fine. I drove it away, and it was fine for a week. I even called him and said, "all systems go".

Then it did it again this afternoon.

Does anyone have a definitive solution? I've dropped $1500 in about 3 weeks, for what seems like nothing. So far in this EXCELLENT thread, I've read about U-Joints, Steel belts in the tires, and Power Steering pump. I plan on suggesting these things to the mechanic Monday morn.

Any other suggestions?

 

Since I posted this in the middle of the night I'm bumping it to increase the chance of visibility.

 

It's either the PS pump or the u-joints and I changed both at the same time unfortunately but it HAS TO BE one of the two. Next time it does it pull over on a gravel shoulder, turn it lock to lock, and it will go away temporarily. I actually just doused the joints with penetrating oil.

 

I'm also not a mechanic, but I would highly suggest a new pump.

 

Could you elaborate? What leads you to think it's the PS pump as opposed to the siezed U-Joint others are citing as the culprit?

 

Because the pressure affects the spool valves inside the steering box. I would just throw a rebuilt pump in there first.........cheap-easy.

 

Couldn't have said it better. For me, my experience says that when a problem comes and goes, it's an "active " device. In this case the pump is the active. The pump pressure can very, and sometimes work just fine. If it was a U-joint, or ball joint, or tie rod or, Pittman arm or something... They usually don't suddenly straighten up and fly right, and work for a week. Power steering pump, or sump pump in the house crawl space, when they start to die, they don't always just stop working completely. I believe you are getting your warnings from the pump that it is on it's way out.

I'm a cable guy by trade, so any actual mechanics with some advice would know better than me, just my opinion.

 

I had the same symptoms.
Is your truck 4x4?
If it is ,when it will start to jerk switch to 4x4 for a moment and report back.
That's how I knew my u-joints are shot.

 

I like the way this guy thinks. Sound reasoning, good advice.

I have been following this thread just to see where it ends up. Hydraulics can be a nightmare when we don't know what makes them work. I don't have a clue what is inside the steering box, where or what kind of valves there are, but the smallest bit of trash can wreak havoc.

Pump output may be the problem as well as the steering box.

 

A lot of people replaced the PS box but it didn't help. Mine is still there at 165k miles and works perfectly.

 

I encourage everyone who has experienced the problem SPECIFICALLY outlined at the outset of this thread to heed the advice of those suggesting the front-end U-joints at the culprit.

The U-joints LOOKED fine, so they were initially OVERLOOKED by the mechanic as a cause of the steering malfunction. But based on the advice found in this thread, I asked him to take another look. He locked the hubs and watched the U-joints as he turned the tire. Sure as heck, they reached a point in the rotation where they bound up. It SHOULDN'T happen, but it does, and that is why this answer is non-intuitive.

If you come out of a turn, and suddenly your steering jerks in the direction of your turn, and trying to correct it takes the wheel past center, jerking it the other direction, and you wind up not being able to steer straight, turning the wheel from left-to-right, never being able to center it - if stopping and turning the wheel from lock-to-lock temporarily solves the problem - the very first thing you should look to is your front-end U-joints.

After a few very frustrating weeks of misdiagnoses and un-needed repair on worn-but-still-functioning steering components, and still having this intermittent problem resurface, I had the U-joints replaced. I drove the Excursion with 19.5' fiberglass boat in tow 500 miles to Lac Seul over some rough terrain, and my problem is GONE.

Thanks to those on this thread who crowdsourced the solution to my problem.