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91 LS400 Power Steering Dead at Idle

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Old 07-31-14, 03:00 AM   #1
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Default 91 LS400 Power Steering Dead at Idle

I just got this as an replacement for a family members prior LS400 (92-93)

The issue is at idle there is no power steering, rev it to about 1k and poof normal operation (I've drove 92-93 for years....)

Please tell me that doesn't sound like the rack & pinion, etc. It sounds more to me like the pumps pressure isn't maintained (Also no sound on the engine as if no load due to PS btw) so pump is out of efficiency I hope. Potentially due to "screens" I read, or low fluid.

Going to check PS level out tomorrow, car is gorgeous- 160k miles. Only issue was pretty much the power steering, flawless interior. I have yet to read much about this issue, more so the leaks, etc

If you guys think it just needs new pump, awesome. I'll be doing that in a few days, going to try topping off the fluid, having it be flushed, then pump replace.
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Old 08-03-14, 09:52 PM   #2
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pump is bad or reservoir could be dirty which it isn't allowing the pump to circulate the fluid fast enough. that's why when you give it gas the pump moves fluid faster.
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Old 11-29-14, 11:28 PM   #3
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Did you check if the "idle air control valve" that is bolted to the side of the power steering pump has been removed/deleted and replaced with a bolt/plug, also if it has been removed the vacuum lines that were originally connect to it should have been plugged. When the power steering is under a heavy load, like when you turn the steering wheel while parked. The "idle air control valve" is what idles up the engine when P/S pump needs more power.

A new "idle air control valve" is about $120 and are made of plastic that are prone to fail and leak PS fluid (ATF fluid) everywhere and directly onto alternator eventually causing failure.That is one reason why many people delete the "idle air control valve" and make sure their idle rpm is to 700+ to prevent engine stall while cranking the steering wheel at a stop, like when parallel parking.
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Old 11-29-14, 11:28 PM

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