Harsh riding '05 LX this can't be normal

[RoderickGI]

Sounds like a perfect set up. What coils do you use? Any specs re load carrying, thickness, length, etc, compared to the original coils?

It is a pretty good setup, although the ride isn't as good as it was when the LX was "new" (I bought it at two years old).

I had ARB replace the standard rear springs with OME 862's when I had all the extra weight added. At the time (2003) I didn't know all that much about the AHC, but I knew that I needed to support the extra weight at the rear. I asked ARB about cranking the TBs at the time and they said that they hadn't touched them, and implied it wasn't needed. Wrong! Anyway, the OME 862 springs have the same free length as the original springs, which was what I wanted because I didn't want a lift. I'm sure you can find the specifications for 862's on the web somewhere.

As per this post here I would probably consider air bags to support the extra weight if I did it all again, but at the time air bag technology just wasn't good enough, or available locally, and I couldn't find a suitable solution. I would probably still use rear springs stiffer than the originals, but not as stiff as the 862's.

The front Actuator Spheres are pre-charged to 450 psi, and the AHC pressure at Normal height is 500 psi, as compared to the standard FSM value of 825 psi.

The rear Actuator Spheres are pre-charged to 500 psi, and the AHC pressure at Normal height is 550 psi, as compared to the standard FSM value of 683 to 839 psi.

Those values are with both fuel tanks full: 96 Litres standard and 182 litre Long Ranger. I haven't worked out what the extra carrying capacity is due to lowering the normal working pressure, but as you can see I have picked up about 300 psi front and rear to carry extra load over the standard values.

I haven't changed any of the dampening valves in the Actuators (I wouldn't want to do that), but I run the damping on the Normal setting around town when unloaded, and stiffen it up when loaded and on mountain trails. This works fine.

The front suspension is a little "eager" (bouncy) with the above settings when the LX is unloaded, so I am considering backing off the TBs by one turn, which is equivalent to adding about 45 psi to the AHC pressure. That would still work fine, since the weight on the front doesn't increase as much as the rear when I load the LX up.

With this setup, the LX will still lower down to the Low postiion (although AHC pressure is near zero then), and will raise to the High position, so I don't lose anything there.

 

[RoderickGI]

how do you properly index a torsion bar? my torsion bar adjusting bolt isnt the same and how to read the ahc pressure using lspv when in fact the front pressure from left to right seems to be conected

If you search around here you should be able to find some PDFs of the relevant FSM pages for measuring the AHC pressure and adjusting TBs. I'm pretty sure they have been posted before. I just have a hard copy version, and no working scanner.

I'm not sure what you mean by "my torsion bar adjusting bolt isnt the same". The mounting brackets on each side are slightly different, and the height from the top of the bracket to the top of the bolt is different on each side, but the bolts are the same. The FSM gives values for the range of adjustment allowed, but the TBs must be set to get the correct AHC pressure.

The front left and right AHC fluid lines are indeed connected and have the same pressure, at least while the front wheels are straight. You only need to measure the pressure on one side at the front, although I measured both and found some differences due to friction.

 

[vxlc80]

If you search around here you should be able to find some PDFs of the relevant FSM pages for measuring the AHC pressure and adjusting TBs. I'm pretty sure they have been posted before. I just have a hard copy version, and no working scanner.

I'm not sure what you mean by "my torsion bar adjusting bolt isnt the same". The mounting brackets on each side are slightly different, and the height from the top of the bracket to the top of the bolt is different on each side, but the bolts are the same. The FSM gives values for the range of adjustment allowed, but the TBs must be set to get the correct AHC pressure.

The front left and right AHC fluid lines are indeed connected and have the same pressure, at least while the front wheels are straight. You only need to measure the pressure on one side at the front, although I measured both and found some differences due to friction.

what i mean about not the same is that my passenger side adjusting bot is tighter or more thread in compared to the driver side which has more thread out

 

[RoderickGI]

Mine are different left to right as well, by a noticeable amount, although not too much. I think it just comes down to differences in the Torsion Bars spring rate.

When your steering wheel is straight, the front left and right side of the AHC are connected hydraulically, and receive the same pressure of fluid. Therefore, the AHC provides the same amount of lift on both sides. To balance the TBs left to right, all you can do is make sure that the height of the vehicle is the same on both sides. That implies that the TBs are providing the same (or the correct amount of) force to lift the vehicle. I haven't found any other way to match the settings of TBs left to right, although the FSM shows the range of adjustment to expect, and it is different left to right.

 

[vxlc80]

Mine are different left to right as well, by a noticeable amount, although not too much. I think it just comes down to differences in the Torsion Bars spring rate.

When your steering wheel is straight, the front left and right side of the AHC are connected hydraulically, and receive the same pressure of fluid. Therefore, the AHC provides the same amount of lift on both sides. To balance the TBs left to right, all you can do is make sure that the height of the vehicle is the same on both sides. That implies that the TBs are providing the same (or the correct amount of) force to lift the vehicle. I haven't found any other way to match the settings of TBs left to right, although the FSM shows the range of adjustment to expect, and it is different left to right.

noted. will double check my torsion bars nextime

 

[TheDough]

BACK FROM THE DEAD.. I have been working on my new to me 2003 LX to get things in order and cranked on the TBs to get he pressures inline after fluid flush.. cranked them a little too much and the now the ride is harsh so I will be backing them off a bit...

I am also curious about how tight each of the TBs should be.. If anyone has any FSB inf or guidance on how to setup the TBs it would be appreciated.

 

[PADDO]

The TBs should be tightened/loosened to give a front neutral pressure of 6.9MPa via Techstream. Search "AHC FSM" and you'll get hits on the FSM neutral pressure adjustment .pdfs I've posted previously.

 

[TheDough]

The TBs should be tightened/loosened to give a front neutral pressure of 6.9MPa via Techstream. Search "AHC FSM" and you'll get hits on the FSM neutral pressure adjustment .pdfs I've posted previously.

PADDO, thank you for the feedback and for your valuable input.

As I cranked the TBs to bring the globe pressure down (from a high initial 8.4 mpa-g reading) after flushing the system on my new to me 72k mile 2003 LX, down to 6.4 front and 6.8 rear, the ride became quite harsh. I backed them off a bit and now the reading is 7.2 front and 6.9 rear but the ride still seems off somehow.. When I first begin driving after the car has been off, the ride with the setting one notch up from comfort is good and feels right, but after driving 10 minutes or so, it feels as though something has changed and the ride feels much harsher over small bumps and imperfections. It still feels smooth over large dips and bumps but small imperfections and cracks in the road are harsh. I drive mainly in the NYC metropolitan area and the roads are terrible. With the accumulator pressure setting close to where they should be now, I am wondering what is going on. I am thinking of disconnecting the battery for an hour or so so that all the systems in the car can reset themselves, or perhaps doing another AHC fluid system flush.. I may have sucked a little air into the system which could be causing this..

There are no techstream faults. Does anyone have any advice?

Thanks in advance

 

[PADDO]

Have a look at the thread "definitive list of AHC maintenance items" starting at the end and working backward as it's quite lengthy now. Essentially start with the basics: tire pressures, fresh fluid with no air/gas, vehicle front and rear height, cross level, front and rear neutral pressures (try 6.7 front/6 rear works for me). You'll need to get that rear pressure down (if you're at spec height now) with new coils (add spacers whilst you're down there). Do the Low to High reservoir graduation check because if you're still on the original 03 damper globes they are nearing the end of their serviceable life and no matter how good your neutral pressures are if the globes are done then you'll never achieve acceptable damping. By ensuring your neutral pressures are at their optimum (not "in spec" but optimally adjusted) you'll get the most out of your aging globes, if you can get pressures of front 6.7ish/low 6s rear and 9+ graduations on the reservoir test your damping should be OK, not like new (14 graduations) but acceptable.

 

[tamc79]

In a similar situation with a harsh ride, and loss of ride height, I just took my 2004 LX to IPOR and had the AHC suspension converted to an OME 2" lift. Less than half the expense of most repairs on the height adjustable suspension and more reliable long term. The lift is not extreme, and the ride is similar to my 2001 Landcruiser with non-AHC suspension.

 

[TheDough]

It feels as though there is some sort of signal going to the system to make it firm up. After driving 10 minutes or so, or getting up to 30+ miles per hour (which sometimes takes 10-15 mins for me as I do alot of city driving) the ride changes from what I would expect.. to the bouncy and firm ride over small bumps and cracks.. Im going to disconnect the battery for a while to see if that has any effect on resetting any electrical system. If that doesn't do anything I will back the TBs off a bit to see if I an get that smooth ride back and consider doing another flush and see what happens. I want that soft ride back.

 

[PADDO]

There are signals constantly going to the front and rear dampers when you're moving! that's the Adaptive part of Adaptive Variable Suspension. Damping is dynamic and speed dependent, in conjunction with feedback from the height sensors (and several other inputs). You can monitor the signals going to the front and rear damper control valves whilst driving, and in your case that would be a worthwhile exercise, but you need Techstream. You can also monitor the height sensor feedback too, to ensure you're not creeping up in height and thereby increasing neutral pressures at the expense of your damping. You may well have a temperature related problem - changes in viscosity or changes due to the expansion of entrained gas would need to be ruled out. A simple way to determine if your problem is most likely hydraulic/mechanical or electronic control is to put the system into the 16 step test mode but lock it in step 1, the softest, and go for your normal drive. If the ride becomes harsh then you can be pretty confident it's a hydraulic/mechanical issue and then you can focus effort in that direction. You can depower the AHC ECU by pulling the 20A AHC IG fuse, no need to pull a battery lead.

 

[TheDough]

Hello all...

So I bled my AHC system again thinking there might be air, and my firm ride still persists. The truck handles big bumps and dips just fine. It passes the curb test fine which makes me think the globes are ok. Ride heights are good and globe pressures are good. Goes up and down fine but It feels as though the truck is locked in sport mode..

I have C1721 and C1723 codes (damping force control actuator) present and cannot seem to clear them.

I had the truck up on the lift the other day and as I was looking around I noticed some damaged, melted wiring on the passenger side running from the rear globe to the rear shock along the top of the frame. I think I finally found my issue.. I have not yet had the chance to try and remove this wiring harness. Has anyone ever encounterd anything like this before...? I can't think of how these wires got damaged.. Seems that there in a leak in the a/c line just above these wires... Could the leaking freon (or equivalent) have damaged or melted these wires? I'm hoping I can remove and replace this wiring and it will solve my problems. If anyone has any info to share that could be helpful, I thank you in advance.

 

[TheDough]

Turns out an exhaust leak that I put off fixing for a few months melted the harness! I discovered this after speaking to a Lexus tech who has seen this before.. At least the mystery is solved.. now to replace the harness.. Im am excited to get my smooth ride back!

This is a great example of why it is important not to delay repairs.. I will add it to my book of wisdom.

 

[DirtDawg]

Turns out an exhaust leak that I put off fixing for a few months melted the harness! I discovered this after speaking to a Lexus tech who has seen this before.. At least the mystery is solved.. now to replace the harness.. Im am excited to get my smooth ride back!

This is a great example of why it is important not to delay repairs.. I will add it to my book of wisdom.

Glad you found your problem! Depending on the price of he harness, you might just want to splice your current harness back together.

 

[uHu]

Pics?
or Where exactly?
And yes. A good waterproof splice is normally faster than replacing harness.