Rhambler

I'm really, really curious about our engine's idle RPM speed while in drive and stopped with low to no accessory loads (i.e., AC, seat heaters, etc.).

In my case, a brand new car, it idles low while in D and stopped with little to no accessory loads. It is, by my estimate, at 450 RPMs. Turn on the AC and this jumps to over 600 RPMs.

So please share your results in this confidential poll and please don't hesitate to add any comments or feedback. If you select less than 500, please choose one of the bottom two choices. You can select multiple items in this poll.

The categories are:

2007-2012 Engine RPM while stopped, in Drive and no AC/Seat Heaters/Defrosters, etc.
1. Greater than 600 RPM
2. Less than 500 RPM


2013-2016 Engine RPM while stopped, in Drive and no AC/Seat Heaters/Defrosters, etc.
3. Greater than 600 RPM
4. Less than 500 RPM

Do you feel slight vibration if you answered less than 500 RPM?
5. Yes
6. No

Thank you.

Rhambler

Thanks for those that entered data. Anymore care to share?

Thanks again!

nsaldanh

I had this issue on a 2012 LS. Dealer told me that when Lexus designed the car they assumed that either the AC or the headlights or the seat cooler fan would be on at all times. If all of them are off the RPM drops below 500 and that's when you get the vibration. If you turn any one of them on the RPM goes above 600 - 650 and the vibration goes away. I now have a 2014 LS and I leave the seat cooler in auto mode and the RPM never drops below 600 when idling - and there's no vibration either.

Rhambler

Yeah, we kind of came to that conclusion ourselves.

Although, I have no idea why they made that assumption, as reasonable as that assumption may be. I'm sure they tuned the engine with the worst-case scenario in mind, being the LWB with executive seats and having a constant, heavy load. Assuming some fat cat in the back sucking on AC or massaging chair nonstop is fairly reasonable I guess. However, us with the standard model got the same engine, same exact tune, regardless of the fact that the amount of potential accessory load is much, much less.

Adjusting the fuel/air map under various engine load scenarios--including no accessory load--wouldn't be that hard I would imagine. The only drawback is fuel economy, albeit a customer buying this car, even the base one, probably wouldn't care that much. Just seems lazy.

In any case, please share your experience if you wouldn't mind.

Doublebase

Personally for me, I don't think I've ever seen an engine idle so low and still be able to run smoothly. It certainly doesn't bother me. I can't remember a time when my idle was rough, or the engine stumbled, regardless of the low rpm.

roadfrog

Ditto, no matter how low my idle goes, it does not vibrate...AT ALL.

Rhambler

The low idle RPM vibration is more of a resonance shudder. It's not like the entire car vibrates, but it something that is felt in the seat of the pants, so to speak, when idle RPM drops to 400-500 RPM. No noise is associated with it, the car is still tomb quiet.

Again, it's probably somewhat subjective and different people will perceive it more than others I'm sure, but it is noticeable, at least to me and others that have reported it.

However, as stated, this shudder disappears entirely when idle RPM goes up with comparable accessory loads.