Suspension Problem 1998 LX 470
05-11-04, 11:18 PM
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Suspension Problem 1998 LX 470
Recently the LX has developed a problem (or maybe 2 separate ones).
1) Frequently when I stop (street driving), the car drops, and then immediately jumps back to the correct height. Usually both back and front at the same time, but sometimes one after the other.
2) On some roads, the car becomes very bouncy, similar to a shock absorber problem, (front shocks were replaced 6 months ago).
One thought I had is that the suspension system is over pressurising, maybe due to a sticking valve, and then suddenly releasing and repressurising to the correct height.
Any ideas?
email ron.thompson@sumitomocorp.co.jp
1) Frequently when I stop (street driving), the car drops, and then immediately jumps back to the correct height. Usually both back and front at the same time, but sometimes one after the other.
2) On some roads, the car becomes very bouncy, similar to a shock absorber problem, (front shocks were replaced 6 months ago).
One thought I had is that the suspension system is over pressurising, maybe due to a sticking valve, and then suddenly releasing and repressurising to the correct height.
Any ideas?
email ron.thompson@sumitomocorp.co.jp
05-12-04, 04:51 AM
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Ron, I remembered reading something about this problem before. My 470 will adjust heights (level out then raise) when I come to a stop from higher speeds but that is because it lowers an inch at highway speeds and is just readjusting for lower speeds I believe. Here is the thread I remembered click here . I have noticed that my LX will go into sport suspension mode at times when I am on comfort. I have no explanation for it. Maybe the thread I mentioned will shed some light on the computer issue.
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05-12-04, 10:25 PM
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I had a look at the other thread, and it helped a bit. They seem to concentrate on computer, rather than a sticking valve.
I've also tried setting the suspension on one harder than comfort, and I don't seem to get the dropping/raising when I stop. Maybe it's cured?
Oh for the days of the Ford Anglia, when I could fix anything with a hammer, a screwdriver and some duct tape!
I've also tried setting the suspension on one harder than comfort, and I don't seem to get the dropping/raising when I stop. Maybe it's cured?
Oh for the days of the Ford Anglia, when I could fix anything with a hammer, a screwdriver and some duct tape!
05-15-04, 04:08 AM
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Howdy folks, I believe that original thread on suspensions weirdness was the one I started.
New understanding of my particular issue, FWIW:
It only happens on one particular stretch of highway, I-20 east of Birmingham near Anniston, AL. That stretch of road is terrible, with severe washboard effect from the poor condition of the concrete roadway. Basically, there is an excessive bump at the joint between each concrete slab, and it extends for miles.
At highway speed, it causes a high-frequency AND high-amplitude excitation of the suspension: Thump-thump-thump-thump-thump.....several thumps per second, continuing uninteruppted for 10 or 15 minutes straight. And it's high-amplitude: Fairly large bumps.
My theory:
I believe that this road causes the LX470 suspension sensors to pump an overly-large flood of data, because the suspension components are traversing through a large range of travel, very quickly, up and down at a high frequency, repeat ad infinum. And continuing over a long enough time, it eventually just overloads the sensor input memory buffers of the suspension computer ("stack overflow"). Computer then crashes, and goes into default "limp" mode, which happens to be "Full Sport" or the firmest setting, in this case.
(BTW, this is similar to one technique used by hackers to crash computers - stack overflow caused by data flood. I've seen it myself with port scanning tools flooding a router with excessive data scans.)
I did check out the suspension computer, per the Service Manual, as far as I could without the special Lexus Diagnostic Tool. Found no problem. And the issue ONLY occurs on that one stretch of terrible I-20. So I think that this issue is probably just a design shortcoming, and I'll bet that the newer ones don't have this problem, if Toyota/Lexus historical pattern holds true.
As to the other issues noted with raising/lowering the height inexplicably - I've seen my height change without apparent reason before, say, sitting at a stoplight or something - but I figured it was just adjusting as normal. It does do height control normally (unless set to "OFF" by dash switch), so it surely will tweak vehicle height from time to time, especially noticeable if it waits for vehicle to slow or stop to do so.
A related item: When towing a trailer, the LX will raise the rear of the vehicle to counter the trailer tongue load and keep the LX approximately level, and it will lower it again to re-level the LX when the trailer load is removed. So, the height control also includes vehicle level control, and it will indeed produce a few inches of raise/lower effect, as I've seen myself. (A very nice feature to have when trailering, I might add.
More comments welcome.
New understanding of my particular issue, FWIW:
It only happens on one particular stretch of highway, I-20 east of Birmingham near Anniston, AL. That stretch of road is terrible, with severe washboard effect from the poor condition of the concrete roadway. Basically, there is an excessive bump at the joint between each concrete slab, and it extends for miles.
At highway speed, it causes a high-frequency AND high-amplitude excitation of the suspension: Thump-thump-thump-thump-thump.....several thumps per second, continuing uninteruppted for 10 or 15 minutes straight. And it's high-amplitude: Fairly large bumps.
My theory:
I believe that this road causes the LX470 suspension sensors to pump an overly-large flood of data, because the suspension components are traversing through a large range of travel, very quickly, up and down at a high frequency, repeat ad infinum. And continuing over a long enough time, it eventually just overloads the sensor input memory buffers of the suspension computer ("stack overflow"). Computer then crashes, and goes into default "limp" mode, which happens to be "Full Sport" or the firmest setting, in this case.
(BTW, this is similar to one technique used by hackers to crash computers - stack overflow caused by data flood. I've seen it myself with port scanning tools flooding a router with excessive data scans.)
I did check out the suspension computer, per the Service Manual, as far as I could without the special Lexus Diagnostic Tool. Found no problem. And the issue ONLY occurs on that one stretch of terrible I-20. So I think that this issue is probably just a design shortcoming, and I'll bet that the newer ones don't have this problem, if Toyota/Lexus historical pattern holds true.
As to the other issues noted with raising/lowering the height inexplicably - I've seen my height change without apparent reason before, say, sitting at a stoplight or something - but I figured it was just adjusting as normal. It does do height control normally (unless set to "OFF" by dash switch), so it surely will tweak vehicle height from time to time, especially noticeable if it waits for vehicle to slow or stop to do so.
A related item: When towing a trailer, the LX will raise the rear of the vehicle to counter the trailer tongue load and keep the LX approximately level, and it will lower it again to re-level the LX when the trailer load is removed. So, the height control also includes vehicle level control, and it will indeed produce a few inches of raise/lower effect, as I've seen myself. (A very nice feature to have when trailering, I might add.
More comments welcome.
Last edited by Bobhgd; 05-15-04 at 04:17 AM.
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05-15-04, 04:55 AM
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Don't see how it can be a design fault as it's just started after 2 years of no problems. It happens fairly randomly, and the dropping/rasing may not be connected with the bouncy ride.
05-16-04, 04:38 AM
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Hey Ron,
The "design shortcoming" I mentioned was pertained to issue of the height position sensor data overflow causing the computer to crash and go into full-stiff mode - NOT the erratic (?) raise/lower issue that you mention.
As you note, if you have a problem that is just starting after 2 years service of the vehicle, then that is a different thing altogether.
Good luck with your issue.
The "design shortcoming" I mentioned was pertained to issue of the height position sensor data overflow causing the computer to crash and go into full-stiff mode - NOT the erratic (?) raise/lower issue that you mention.
As you note, if you have a problem that is just starting after 2 years service of the vehicle, then that is a different thing altogether.
Good luck with your issue.
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