the power steering strikes back

[Redskull]

Lately, my power steering has been exhibiting some wild problems, that I can only diagnose as being possessed by demons. The first thing I noticed was alot more noise during assist: like a cross between a hissing and a gurgling. Then I noticed that the further I try and turn the wheel, the more of a fight the system puts up against it. This is where things get funny: If you let up slightly, the system will provide a pretty hard 'kick' putting the wheel back to center. But if you *increase* the turn slightly, the system will provide a nice kick in the direction you want to turn, before it starts fighting you again. To make matters worse, it also seems related to engine speed. If i'm sitting still, with the wheel turned slightly enough to engage the assist, and then goose the engine a few hundred RPMs, the 'fighting back' dissapears and I get a kick in the direction of the turn. But when the RPMs come back down, the 'fight back' increases, and the wheel turns itself back to where I originally had it. The fluid is full, the air has been purged, and I got a new pump about a year ago. I was thinking maybe a malfunctioning check valve? Has anybody else ever had this problem? Can anbody recommend any troubleshooting steps to isolate what the problem might be?

alan

 

[SHOBlu]

Redskull, I found a couple of things out for you. First check the Power Steering Pressure Switch (PSP). The Power Steering Pressure (PSP) switch sends an input signal to the Powertrain Control Module (PCM) when the power steering pressure rises above 400-600 psi. The PCM uses this signal to adjust idle speed to compensate for additional load on the engine.

Second, if your vehicle has Variable Assist Power Steering (VAPS) this could be your problem.The VAPS Module controls the power assist levels based on the vehicle speed.The VAPS module sets the position of the variable assist stepper motor according to the vehicle speed sensor signal.

I think its a VAPS problem your describing. Other than knowing about how the system works is all I can help you with. Hopefully others know how to go about pinpointing the exact problem in the system.

 

[bertha66]

I had a 92 GL wagon with the VAPS that was doing something like this, when I pull the steering rack out to change it, I fond that the wires to the module were broke. I fixed the wires and replaced the rack, sense it was out anyway. It has been working good sense. Now my 93 SHO is begining to do this also, just starting, so as soon as I can I will pull the SHO's rack and check it also.

 

[Hank F.]

I have the same problem. How do I determine if I have variable assist?

 

[AREA 91]

What year is your SHO?

 

[Hank F.]

93 Atx

 

[93rev2sev]

If your rack has electrical wires, you have VAPS...I think

 

[sho93]

All 93+ SHOs have VAPS.

I had a slight tugging with my system. Changing the fluid weekly until it stayed clean almost completely solved the problem.

 

[SHOtimer]

All 93+ SHOs have VAPS.

I had a slight tugging with my system. Changing the fluid weekly until it stayed clean almost completely solved the problem.

I was just about to say the same thing. A lot of problems come from having old decayed fluid in there. Some of these SHO's are still running around with original fluid.

Suck the fluid out of the resivor and refill it. Do this every other day untill the fluid stays clean (Usually takes a few weeks). Mobil 1 Full sythentic ATF fluid works great in these systems.

Doug

 

[Redskull]

awesome, i'll give the fluid a try. It's certainly easier than tearing out the rack. Also, this might be a stupid question, but in the shop manual, the VAPS self-test says to 'rotate the steering wheel for 90 seconds, noting any changes in effort'. Do they mean continuously turn it back and forth, or just rotate it and hold it?

alan