AHC Front end drop (6 Viewers)

[jmj2323]

I went on my first road trip with my 2001 LX470 since I picked it up a month ago. We pulled through a drive-thru and pulled up to wait for 10-15 minutes for our food and it while sitting in park it felt like the front end just dropped at least an inch, maybe 2. I got out and looked and it seemed like there was some front end rake. After that I lowered and raised it, no problems, but I still get the sense the front end is lower than.it was/should be. Anyone else experience this?

 

[IndroCruise]

I went on my first road trip with my 2001 LX470 since I picked it up a month ago. We pulled through a drive-thru and pulled up to wait for 10-15 minutes for our food and it while sitting in park it felt like the front end just dropped at least an inch, maybe 2. I got out and looked and it seemed like there was some front end rake. After that I lowered and raised it, no problems, but I still get the sense the front end is lower than.it was/should be. Anyone else experience this?

This may just be the AHC system doing its normal thing and auto-adjusting the Front and Rear heights in response to the Height Control Sensor positions. This can happen when idling with the vehicle stationary -- and the system "notices" that heights require auto-adjustment -- such as after braking, crossing a spoon drain at entry to a drive-thru, etc, etc.

The Front height measured by tape-measure from hub centre to fender lip vertically above should be about 19.75 inches; Rear hub-to-fender height should be about 20.50 inches -- although the Previous Owner may have set different heights, or the vehicle may have been "lifted".

Preferences vary but you could expect Rear to Front rake of about 1 inch. The hub-to-fender measurements are the important things.

If the Front is permanently low and will not respond to the LO - N - HI height selector on the centre console, and/or rough ride is being experienced, then it is time to look for other problems, with suspicion falling on the adjustment or condition of the Height Control Sensors.

 

[ramangain]

Check your front pressure during the L to N test using Techstream. After setting that pressure to 6.7 MPa, my truck has yet to do the random height drop and recovery that you experienced.

 

[jahawk]

This may just be the AHC system doing its normal thing and auto-adjusting the Front and Rear heights in response to the Height Control Sensor positions. This can happen when idling with the vehicle stationary -- and the system "notices" that heights require auto-adjustment -- such as after braking, crossing a spoon drain at entry to a drive-thru, etc, etc.

The Front height measured by tape-measure from hub centre to fender lip vertically above should be about 19.75 inches; Rear hub-to-fender height should be about 20.50 inches -- although the Previous Owner may have set different heights, or the vehicle may have been "lifted".

Preferences vary but you could expect Rear to Front rake of about 1 inch. The hub-to-fender measurements are the important things.

If the Front is permanently low and will not respond to the LO - N - HI height selector on the centre console, and/or rough ride is being experienced, then it is time to look for other problems, with suspicion falling on the adjustment or condition of the Height Control Sensors.

My truck does this as well. I wouldn't be overly concerned.

Jim

 

[Beto Cruiser]

Agreed. My truck drops the front anytime I'm at a stoplight on an upward incline, and all my pressure are in spec (I do have max AHC lift though). It's doing it's job trying to make you level, albeit a bit abruptly.

 

[RoughOne]

I actually enjoy the feature!

 

[jmj2323]

Agreed. My truck drops the front anytime I'm at a stoplight on an upward incline, and all my pressure are in spec (I do have max AHC lift though). It's doing it's job trying to make you level, albeit a bit abruptly.

Thanks everyone for the info. I love the AHC features and ride. What does it mean to have the max AHC lift? I would like to be able to keep it at the high setting at any speed- is that a possibility?

 

[Beto Cruiser]

Thanks everyone for the info. I love the AHC features and ride. What does it mean to have the max AHC lift? I would like to be able to keep it at the high setting at any speed- is that a possibility?

By max lift I mean manipulating the height sensors without cutting them. Here are some good threads on AHC lifts:

2-2.5" AHC Lift Using King Coils & Shock Spacers

Well all my parts finally showed up and this past weekend I lifted my LX. My goal was to have a 2-2.5" lift (using the AHC system), while keeping close to stock travel characteristics and stock neutral pressures. Components Installed: KING KTRS-79 Coils (sourced from eBay seller sparesbox_auto)...

forum.ih8mud.com

AHC Sensor Adjustment for Lift

Adjusting your AHC sensors are fairly easy :)banana: job). You'll need to furnish/fabricate a simple bracket extension which I'll cover in step 5. You'll also need one can of AHC fluid from Toyota $22/can. (part # 08886-01805). I have heard the exact fluid costs more if bought from Lexus. 1...

forum.ih8mud.com

Pretty much it's just adjusting the sensor to make it think you're lower to the ground than you are. You can take it a step further with modifying the sensors and some other adjustments, but I didn't feel that was necessary.

With the sensor lift you still get the same boost going to high, but it doesn't mean you're always at high. I think Slee or someone sells a product that overrides the speed limit for high mode (30 mph ish I think before it drops you back), but I wouldn't recommend it unless you really think it's necessary. A modest sensor lift with the option to go to high mode when needed is perfect.

 

[jmj2323]

By max lift I mean manipulating the height sensors without cutting them. Here are some good threads on AHC lifts:

2-2.5" AHC Lift Using King Coils & Shock Spacers

Well all my parts finally showed up and this past weekend I lifted my LX. My goal was to have a 2-2.5" lift (using the AHC system), while keeping close to stock travel characteristics and stock neutral pressures. Components Installed: KING KTRS-79 Coils (sourced from eBay seller sparesbox_auto)...

forum.ih8mud.com

AHC Sensor Adjustment for Lift

Adjusting your AHC sensors are fairly easy :)banana: job). You'll need to furnish/fabricate a simple bracket extension which I'll cover in step 5. You'll also need one can of AHC fluid from Toyota $22/can. (part # 08886-01805). I have heard the exact fluid costs more if bought from Lexus. 1...

forum.ih8mud.com

Pretty much it's just adjusting the sensor to make it think you're lower to the ground than you are. You can take it a step further with modifying the sensors and some other adjustments, but I didn't feel that was necessary.

With the sensor lift you still get the same boost going to high, but it doesn't mean you're always at high. I think Slee or someone sells a product that overrides the speed limit for high mode (30 mph ish I think before it drops you back), but I wouldn't recommend it unless you really think it's necessary. A modest sensor lift with the option to go to high mode when needed is perfect.

Thanks- I’ll dig into this. So much to learn!

 

[thebeedeegee]

I think it's normal. Mine does it from time to time as well usually after a hard stop or when a couple of people get out of the car with it running. It did it a whole lot more often when my front pressures were out of spec so it may be worth checking those if you haven't