mistrz11

Hello!!!

I have question. I'm owner of Lexus ls 460 from 2008. Today I noticed that when I turned A/C and lights off rpm's are dropping to 500. With P mode is all ok, but when I shift to D and I depress the brake pedal steering wheel and the car shakes. Battery is ok and charging from alternator is 14.20. When I turn on the air conditioning, vibration disappear and RPM's rising to 600/700. The engine is warm (has normal temperature"). Tt is strange to me that when I shift to R I do not feel no vibration.

Is anyone already had such a problem?

PS... sorry for my english.

Rhambler

Yes, I would honestly characterize this as normal. The low idle speed with low accessory load is a strange phenomena. The reports seem fairly consistent and the fixes seem fairly hit or miss based on what I've read.

1. You can just leave the climate control on.
2. You can possibly try resetting your ECU and drive without the AC for a few hundred miles while it learns. I think this can be done by disconnecting the battery, although I would research exactly how first and any warnings that night come with it.
3. Use top-tier gas with good detergents.
4. Or, I haven't tried this yet, but just leave the AC off and just drive it like that for a while (a few weeks or a few hundred miles) and see if the ECU learns.

My brand new car exhibited this, although it got better after 1000 miles. If I turn the AC off, though, the idle speed while in D will drop to 400.

lieup

update!
I noticed the above issues and took the car to the dealer and they replaced both left and right side control arms, engine mounts and transmission mount. No more shaking or vibration when in D mode with A/C off. I hope this will helps other folks! Below is the parts number.

(1) Part# 12371-38050 (Transmission mount)
(2) Part# 12361-38221 ( Engine mount)
(1) Part# 48620-59015 (Arm Assy Right side)
(1) Part# 48640-59015 ( Arm Assy Left side)

Total cost for parts and labor= $3441.97
I've only had to pay $100 out of pocket for deductible.

Rhambler

That's interesting, but can you please report your idle speed while stopped, in drive and the AC off.

Is it 400-500 RPMs? Every line on the RPM gauge is 200 RPMs. Or are you idling at 600+ RPMs with the AC off and associating it as fixed?

In our case the issue is engine speed at idle related.

lieup

Here is the image of the RPM in Drive mode with A/C off.

Rhambler

Thanks. We may be dealing with two separate things, although slightly related.

Your idle RPM with the AC off while in D is the same with the AC on for me and in both cases, no perceptible shaking. However, when we turn the AC off, idle speed drops to 400 RPMs and that's when there's some perceptible shaking.

So it's not necessarily related to the AC per se, but more so at different idle speeds.

A. 600-700 RPMs while idling in drive = no shaking. Doesn't matter if the AC is on or off, but in most cases this idle RPM only happens with high accessory loads and the AC being a big one.

B. 450 RPMs = shaking while in idle. This seems to happen when accessory/engine loads are low, most notably when the AC is off and/or seat heaters off, etc.

I wonder if they disconnected your battery while working or reset your ecu. In any case, we may be dealing with separate issues.

Rhambler

One more request, can you turn everything off, AC, climate control, radio, seat heaters, and take another picture of your idle speed while in drive and fully stopped?

Thanks!

lieup

In additional, my car was shaking when I go past 80MPH. After they replaced the above parts it resolved all the issues. I believed the motor mounts had to do with the shaking.

mistrz11

Hello it is always when I stop on traffic lights or when I'm in the garage. I have 500 rpm when I push breaking pedal without lights and AC/OFF. Car falls into a resonance and shakes it. When I turn lights ON It's ok or AC/ON. In ASO they told me that alternator can be damage.

mistrz11

I'm always using good gasolinone 98 or 100+ octanes on Shell stations

mistrz11

I have 500 when AC/OFF and headlights off and radio

Rhambler

Ditto. I feel that resonance as well while stopped in drive with no AC on. It idles at that value and my car is brand, spanking new.

I almost think they assumed us fat cats, driving this expensive car, will never ever think about being in this vehicle without the automatic climate concierge or some big shot in the back sucking on AC or some messaging chair.

They mapped and tuned the fuel, air and idle speed accordingly. Throttle body, emissions, vibration dampening, fuel injection modes all tuned towards this assumption. Well, the ECU all of a sudden sees a light engine load and goes into a default fuel, air, throttle mode, that just wasn't tuned very well. Just seems strange.

They can either update the ECU to never drop below 600 RPMs while stopped in drive with light engine loads (easy) or tune everything to not "rumble" at low idle speeds (hard). Sure, we'll waste more gas, but eh, easiest way to fix IMO.

mistrz11

Thank you very much for response. I have previously problems like more owners with speed hesistation and I have new software to ECU....

lieup

That image was everything off.

mistrz11

Hello, today I tried to make a test with the engine cold, but then I have 700 RPM, that situation occurs only after driving a few miles when the engine warms up.