AHC with harsh ride

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kgrove

kgrove

10 Year 15 Year
Joined
Jul 23, 2008
Threads
45
Messages
565
I've read most if not all of the recent AHC threads and haven't found my solution. I bought the TechStream software, have pressure within spec front and rear (didn't write the pressures down but they were in spec when I tested them last week), flushed the fluid, etc. The AHC system is functioning just fine as best I can test it (other than a squeal from the pump when reaching max height).

My problem is a harsh ride. The AHC works well on medium and large bumps, but the suspension is transmitting a far harsher ride than it used to for small bumps - more like texture in the road. The best way I can describe it is that rough ride feel you get with tire pressure through the roof or on a car with super low profile tires. Every crack or seam in the pavement seems to pass right through the suspension for a harsh ride where my LC used to ride like a cloud.

Assuming my testing is right and the AHC is functioning fine, what else could I look at? Are there bushings that could be shot?

If it helps - 2007 LC, but low miles (about 60K miles). This seems to have either started or gotten worse when I got a new boat that has a much higher tongue weight than my previous boat. The tongue weight overwhelms the AHC and I'm wondering if the extra weight "crushing the suspension" could have ruined some kind of dampening that used to be in the suspension somewhere. I have to admit I'm not much of a mechanic and don't know much about my suspension design, though I'm picking it up from this board and trying to figure out my AHC.
 
I'm sure SWUtah will tell you to rip it out ;-) No doubt he's smiling because you seem to have done the right things and he probably believes you are demonstrating the unreliability of the AHC. You've not mentioned spending money, so I guess he can't say it's too expensive yet!

You didn't mention how many graduations on the reservoir between L and H... That is one check that tells you if the system is working correctly.

But I'll try to answer your questions as best I know.

There are bushings like on normal shocks. I don't recall if you can replace them easily and I've not heard of anyone doing it, but it just may be - I will take a look at mine tomorrow. Getting to them and looking at them is not that hard for the bottom bolts, but more of an issue for the top ones. Some find getting to the top nuts particularly difficult. People doing that tend to be of the "rip it out" persuasion, so they can use some more gentle persuasion (cutting, bashing, etc) on the damper than someone who might keep the damper or replace the bushing!

One thing PADDO recently mentioned was cycling it (L-N-H) from time to time if it got harsh - he said his has started to get harsh sometimes and this fixed it. Theory is that this moves the fluid around the system, and apparently relieves some harshness perhaps from old oil in the dampers. He also mentioned bleeding any air in the system. He might care to elaborate on the last point if he is reading this.

That said, there shouldn't be any residual affect once you take the boat off.

If the harsh ride is only with the boat on, however, it is likely that whilst the AHC neutral pressure is in spec the actual pressure with the boat is that bit too high for effective damping of some road conditions. No doubt if that is the case the inexpensive helper air bags that support some of the rear load would work well. You can even use techstream to decide how much air to put in them when the boat is on.

Also check for an DTC codes in Techstream.

I doubt whether an overload ruins anything as the system has pressure sensors and automatically goes into L mode to reduce the actual pressures from the overloading - conceivably spheres, valves or dampers could be damaged in some conditions so it is possible, but I wouldn't start replacing schtuff yet.

Other things: what tyre pressures are you running? Do you inflate them for the boat and then not deflate them when the boat is off, for instance?

Anyway, that might be of no help, but it is what occurs to mind.
 
It rides harsh all the time now, not just with the boat. The number of graduations of fluid movement from H to L was difficult to measure only because I couldn't clearly tell where the fluid was in the reservoir, but it looked fine.

The only thing I can think of doing is replacing the globes as that sounds like the most likely culprit, but none of the testing I've done suggests it is required. That's an expensive fix to do on a trial and error basis - prefer having firm knowledge that's the right fix before investing that kind of money.

If I can't come up with any other ideas from the board hear my next step is to double back and repeat the tests I've already done. I'm not exactly a mechanical genius, so maybe I didn't do something right.
 
kgrove said:
I've read most if not all of the recent AHC threads and haven't found my solution. I bought the TechStream software, have pressure within spec front and rear (didn't write the pressures down but they were in spec when I tested them last week), flushed the fluid, etc. The AHC system is functioning just fine as best I can test it (other than a squeal from the pump when reaching max height).

My problem is a harsh ride. The AHC works well on medium and large bumps, but the suspension is transmitting a far harsher ride than it used to for small bumps - more like texture in the road. The best way I can describe it is that rough ride feel you get with tire pressure through the roof or on a car with super low profile tires. Every crack or seam in the pavement seems to pass right through the suspension for a harsh ride where my LC used to ride like a cloud.

Assuming my testing is right and the AHC is functioning fine, what else could I look at? Are there bushings that could be shot?

If it helps - 2007 LC, but low miles (about 60K miles). This seems to have either started or gotten worse when I got a new boat that has a much higher tongue weight than my previous boat. The tongue weight overwhelms the AHC and I'm wondering if the extra weight "crushing the suspension" could have ruined some kind of dampening that used to be in the suspension somewhere. I have to admit I'm not much of a mechanic and don't know much about my suspension design, though I'm picking it up from this board and trying to figure out my AHC.
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Sounds like you're a good candidate for air bags. x2 on logically eliminating any maintenance and "hard" faults. Simple enough - decent fluid, no air in system, correct vehicle height, minimum 7 grads on the AHC tank, correct neutral pressure (6.9F and 5.6 to 6.7R) with vehicle unloaded and full fuel tank, no DTCs. I'm starting to believe that the suspension control ecu may benefit from a reboot every now and again. After all, we agree the engine ecu benefits from a cold reset after routine MAF/throttle body clean, for example, to purge fuel trims etc and we're looking at the same vintage (mid 90s at best) technology for the AHC/AVS. Its accepted practice to do a power down and repower up to clear soft faults/hangups (think microsoft) so why not for all of the vehicles' ecus? You'll loose radio presets and US nav zone search area setting and that's about it I think. Personally I cycle the AHC, and have started switching modes in AVS every now and again. Doesn't hurt and seems to manage that "harshness for no obvious reason" syndrome. There are a bunch of inputs to the suspension ecu damping force control: including bouncing control; harshness control; unsprung vibration control; speed; anti roll; anti dive; anti squat and finally the damping mode select switch so it doesn't seem unreasonable to me that if the vehicle is heavily loaded or otherwise altered from factory the dumb ecu may benefit from a power down and reset. Long way of saying try pulling the 20A AHC IG fuse to reset the ecu and see if it makes a difference. I've previously posted a FSM .pdf for testing and steeping through the AVS settings too.
 
kgrove said:
The number of graduations of fluid movement from H to L was difficult to measure only because I couldn't clearly tell where the fluid was in the reservoir, but it looked fine.
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I use the flashlight on my iphone, turn it on, stick it on top of the reservoir and it becomes blatantly obvious where the line is despite the opaque nature of the 10 year old reservoir plastic. I guess any old work light would do.
 
I too have a harsh ride on my 2003 LX 470 with 60k. I did replace the AHC fluid few weeks back but not much has change. I would be interested to know what might be wrong with your system. I even thought of replacing the front and back shock absorbers.
 
How do you reset the AHC ECU?
By taking of the power from the battery?
 
My 98 is pretty stiff over small bumps. It has newer fluid and about 6-7 notches of movement of fluid in the tank. It likely needs new globes, but for those dollars, I am going to change to a standard suspension or lift whenever it needs new tires.
 
2003lx470 said:
I too have a harsh ride on my 2003 LX 470 with 60k. I did replace the AHC fluid few weeks back but not much has change. I would be interested to know what might be wrong with your system. I even thought of replacing the front and back shock absorbers.
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Don't forget AHC is quite different to coils and static dampers. In short here's where to start:
1. Check graduations between L and H in the fluid reservoir
2. Check for any DTC codes relevant
3. Assuming it is in spec check neutral pressures
4. If neutral pressures out of spec adjust torsion bars until front is in spec, and perhaps spacers, new rear coils or helper air bags to rear

None of these are hard, but it is hard to get the stealers or mechanics unfamiliar with the AHC to do them!

The full details are listed in the AHC maintenance thread. If you've not done this don't spend a dime. It seems rare that. The dampers (they are hydraulic dampers technically not shock absorbers) rarely are at issue.
 
Thanks Actualeyes.

I have a Lexus mechanic who work for a stearship. I will ask him to check my system and will report back. If he doesn't mine, I will either take pictures or a video.

To the administrator, I can't load pictures. I am missing my "security token".
 
2003lx470 said:
Thanks Actualeyes. I have a Lexus mechanic who work for a stearship. I will ask him to check my system and will report back. If he doesn't mine, I will either take pictures or a video. To the administrator, I can't load pictures. I am missing my "security token".
Click to expand...
you can buy the MiniVCI with a hacked techstream software on eBay for a nickel and a dime. It's worth having so you can check the electronic gizmos anytime.

And you need to post a few times before you can upload any pics...not sure of the exact rules, but you get the idea...
 
My AHC is s**t. It's not it's fault per-say. I bought the truck with 69k miles a year ago. I don't remember the ride being awful when I bought it but it sure is now. Both my wife and my brother don't like going anywhere in it. They both get queezy. I love the truck but the ride kills me too, I just don't get unsettled as easily (maybe because I'm driving?). It just bounces like crazy over any bumps as if the shocks were blown.

To be fair, I haven't checked anything or baselined the system; it's a '99 so, despite the low mileage, it deserves to have gone wrong by now. I have noticed that the front always sags into "low" shortly after turning the truck off. I assume that means I should torque the torsin bars.

In my defense I changed countries and am in little mood to apply my skillz.

I appreciate simplicity. Swapping in a standard setup will be the first thing I do once I confirm I can indeed keep the vehicle in this bureaucratic nightmare of a country (France).

Cheers-
 
Phat1842Many said:
My AHC is s**t. It's not it's fault per-say. I bought the truck with 69k miles a year ago. I don't remember the ride being awful when I bought it but it sure is now. Both my wife and my brother don't like going anywhere in it. They both get queezy. I love the truck but the ride kills me too, I just don't get unsettled as easily (maybe because I'm driving?). It just bounces like crazy over any bumps as if the shocks were blown. To be fair, I haven't checked anything or baselined the system; it's a '99 so, despite the low mileage, it deserves to have gone wrong by now. I have noticed that the front always sags into "low" shortly after turning the truck off. I assume that means I should torque the torsin bars. In my defense I changed countries and am in little mood to apply my skillz. I appreciate simplicity. Swapping in a standard setup will be the first thing I do once I confirm I can indeed keep the vehicle in this bureaucratic nightmare of a country (France). Cheers-
Click to expand...

In my experience learning how the AHC works is a good investment, and along with the MiniVCI/Techstream for $30 on eBay gibves you the ability to get the AHC back in spec and riding smooth. None of the AHC maintenance things are expensive. The most complex is replacing the fluid. Nothing is very time consuming.

That said it is not normal behavior to drop when the vehicle is turned off. You need to check the DTC codes (again MiniVCI can help).

All the best with the French. I can't imagine getting the gendarmerie to be interested if they think special attention is warranted!
 
Actualeyes said:
there lieth the lesson! Without knowing them you can't follow. For aAny effective maintenance regime It's worth investing in the MiniVCI and techstream.
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Can't follow what? No lesson learned here, I know how the system works. I can tweak on it, but it likely needs globes. I just don't care to spend a dime or time on the system other than fluid changes. I'm prepared and planning to go to conventional suspension or a lift when it fails.
 
TXLX100 said:
Can't follow what? No lesson learned here, I know how the system works. I can tweak on it, but it likely needs globes. I just don't care to spend a dime or time on the system other than fluid changes. I'm prepared and planning to go to conventional suspension or a lift when it fails.
Click to expand...

Sorry Ipad editing of my post! What I meant was...

If you don't know your neutral pressures you don't know how far to turn your torsion bars up or down and what to do with your rear to get it in spec. You can't really say anything's likely (likely needs globes etc). You also won't know whether it has actually failed (as distinct from just needing minor inexpensive and quite quick and easy maintenance).

Sure, if you want to spend your money and time going to a lift or conventional suspension feel free, but don't think you're doing it because the AHC has failed.
 
I get your point. None of the AHC maintenance is all that expensive or hard to do. My point is, cranking torsion bars, replacing rear springs, replacing fluid, etc is not the end all be all for AHC maintenance or repair. Sometimes parts just wear out and are no good any longer (like on a 15 year old truck like mine). When that day comes, I'm spending that money on a different system. If accumulators were $50 a piece, I would have a different plan.
 
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