My brand new car, with 186 miles on it, does this occasionally at stop lights. A bit unnerving and surprising.

It's barely perceptible, but I looked at the RPMs and it only happens when it drops to 500. As soon as my idle increases back up to 700ish, it goes away.

It doesn't always happen and there seemingly is no rhyme or reason why it idles at certain RPMs when I come to a stop. For example, I actually counted the stops on my last trip and counted the amount of times it happened and over ten total stops, it happened once, lol.

I experimented a bit during my second trip and as soon as I turned on my seat heater full blast, the RPM crept back up to 700 and it went away.

I don't have my AC on.

Anyone know why my car idles between 500 and 700, with 500 exhibiting slight vibrations I can feel on my feet?

 

Please read my thread and text Me if u can ! 3019910425

 

https://www.clublexus.com/forums/ls-...in-gear-3.html

See my response at the end.

 

Curious to know what my 09 should be idling at with the AC off? I'm right around 500rpms at idle and I can feel some vibration too. It's not bad but seems like it should be quieter. I understand that there is some direct injection noise too. Just want to know what to expect as far as idle rpms.

 

Mine is over 600 RPMs at idle, although I left the AC in AUTO/SLAVE mode, so I presume my AC is on all of the time, even in heat mode.

I think the cause of these "issues" is the fact that our engines are rather unique, but unique (in my opinion) in a good way in that they have dual injection. It uses port injection during idle and low speeds (I presume) and direct injection under greater engine loads. However, as a result of this design, the overall "tuning" of the engine under these two modes of operation is very difficult. Imagine drawing up air/fuel requirements for direct injection then having the computer, throttle-body, emissions and other parameters adjust to port injection. I'm sure it is not easy, although I think Toyota did a very good job, notwithstanding the sometimes finicky and frenetic computer learning to adjust user parameters/driving conditions to the dual system at-hand.

Direct injection engines, by themselves, offer great fuel economy, power and emissions capability but suffer (badly) from carbon buildup, especially on the intake valves. Incidentally, this was one of the reasons why I steered clear of that Audi. Having to clean your intake by blasting them with walnut shells every 50k miles was something I did not want to endure.

Toyota engineers had the foresight to keep that port injection, which kept those valves clean and mitigated carbon build-up, but still offer the performance and fuel economy of DI engines. However, the caveat is that it's very difficult to design and tune and is rather expensive to build and one of the reasons few manufacturers do it.

HOWEVER, I just learned that the 2016 C7 class 3.0 liter engine (found on the A6 and A7) was the first by Volkswagen Auto Group (VAG) to offer dual injection. It's funny but there was no formal announcement of this change (I didn't know about until after the fact and it wasn't even shown on the sticker), no hoopla and in fact, very little from Volkswagen (outside of trade publications) and the reason being is that this change is more or less an admission of guilt in regards to the slew of carbon problems experienced by Audi and BMW. Lawsuits were involved and I think it was only very recently that it was resolved and settled by extended warranties and reduced engine cleaning costs. Audi finally came to the realization that the headache of DI by itself far outweighed any additional costs and tuning needed for dual injection engines.


http://forums.vwvortex.com/showthrea...Injected-EA888

http://www.greencarcongress.com/2014...4014-audi.html

 

I typed my response without first reading yours. This is exactly what is wrong with my car...well not wrong, but it's what's happening.

 

Yeah, mine did eventually go away. Although after my short jaunt and someone limited confirmation that it did indeed go away, I put my AC back on AUTO mode, so I haven't reconfirmed anything.

One thing about Direct Injection engines is general smoothness (or lack thereof) and even the article I linked to above mentions that in one of the key points at the end:

I think just the general super high-pressures required of direct injection lends to a lot of these noises and feels. The article also mentioned that the high-pressure fuel pump is still used, in part, during port injection for cooling purposes, even though the fuel is being pumped through the port injectors.

I have no idea if Toyota does the same, but we can assume they do, which means that even under port-injection modes of operation, that high-pressure fuel pump, used for the extremely high PSI requirements of the direct injection, is still pumping, albeit differently or through it somehow. Probably why we can still "hear" it under idle conditions and maybe why it might even be louder under idle (no idea if that's the case) as it's running at a different pressure or mode than under normal operation.

The Audi I test drove also slightly "rumbled" during idle. I remember the dealer started it up and left it running for ten minutes before I test drove it. When I finally got in it was already at full operating temperature and I distinctly remember feeling a vibration (slight) under the seat.

These issues could just be systemic of DI engines and even dual injected engines. Toyota may have "tuned" our engines to run under a certain, assumed load (i.e., high accessory loads) and hence tuned idle speed accordingly. The computer may be seeing a low accessory load and, not having to idle higher, ratchets down, but the fuel system (high-pressure fuel pumps) might just be louder or rougher as it tries to tone down its pressure.

Take my thoughts with a huge grain of salt as I'm not a car engineer and just speculating. The only advice I can give is maybe throw more accessory loads, possibly vary your throttle driving behavior (not necessarily an "Italian Tuneup," which is more or less flooring it), but giving the computer something more to think about, change gas brands, add a lot of techron or, if all else fails, take it back and see if there's something actually wrong.

 

 

 

What is the resolution? My '07 does this. When stopped and in drive, there is very mild vibration. Put it in neutral, you can't even tell the car is running. I often find myself putting the car in neutral at stop lights for this reason. Don't get me wrong, it's not a crazy vibration, just very mild and probably only noticeable to me because I'm super ****. So again, how is this resolved?

 

I don't know about the battery solution. I uses Sea Foam Spray and it helped me. Its the spray you have to spray in the intake.