my 2007 with 73k has started to idle rough at traffic lights. Not horrible, but a noticeable vibration. Rpm's are around 500. If I put it in neutral, rmps go up to about 800 and idle gets better. What could cause a rough idle like this?

Thanks

 

You might need to have the idle reset, it is idling too low.

 

Have you had the Valve Spring recall done yet?

 

Not sure - I bought it used a few months ago.

 

Ok go here http://drivers.lexus.com/lexusdrivers/home to register your car with VIN# and you will be able to acess your cars service history over the years. The valve spring campaign should be listed if the previous owner had it done, if not then the rough idle issue might be linked to the defective valve spring/s.

 

Found out the valve spring recall was done years ago so that should be ok. Must be something else. I have been using regular gas in it since I bought it 3 months ago - could that cause the rough idle?

 

regular and not premium??? not sure if that would be the culprit as usually a lower grade gas the car will retard the timing a lil to compensate but I would check the trottle body sensor see if it is dirty, I am guessing no check engine light or it could be a 02 sensor or bad or old plugs as it is suggested to change your plugs every 50k..

 

Same here.

You'll notice that if you turn the headlights or a/c on the problem is gone.

After doing the valve spring recall fix, they did reset something in the engine/transmission and the problem disappeared for a month or so. Then it came back and never gone.

I keep the headlights and/or a/c on. I just accepted it as the new normal and never bothered to think about it ever since.

 

So you are saying if I keep my headlights on all the time or A/C on all the time my rough idle will go away?

 

That's right

 

Agree with waynedog. With the A/C, headlights, or the seat heaters/fans on the car will not vibrate while in drive. Shut all three off and the rpms drop to 400-500 and it gets a vibration while in Drive. I have put 87K on mine and there is no solution.

 

So has Lexus or another mechanic looked at your car and confirmed that there is nothing that can be done?

 

Update on my ongoing rough idle issue:

* Took it to my local mechanic who specializes in Lexus' and he checked everything out and said there were no issues that would cause the rough idle
* took it to my Lexus dealer. They had it 1/2 day. Did a whole ECM reset, checked everything out. Car still idles rough as described above. Lexus dealer told me when they switched from timing belt to timing chain in the 460 the cars do not idle as smooth and there is nothing that can be done - it is in the design of the car. He said it is due to the timing chain design vs timing belt.

Make sense to everyone?

 

Not really. Relative smoothness at a given level of engine RPM for an engine with a chain vs. a belt I could buy (in theory), though I don't think it's the case in practice as I doubt Lexus would incur such a tradeoff in their flagship.

However, your idle is rough in great part because it is low, and that setting is independent of how the cam shafts are driven (by belt or chain). I have no clue what's at play (and my own LS idles very low only when it's ridiculously cold outside), but that explanation just does not make sense to me.

And by the way, the low idle (400-500 rpm) has happened at night as well, with the headlights on, FWIW.

 

I have similar symptoms - just not the same as you Wayne. My car vibrates when I am stopped at a signal with the lights/seat warmer/AC NOT on. The rpm drops to about 500 and I can feel the vibration in both front seats. I turn on any one item of the three listed above and the vibration goes away immediately -- since the rpm jumps to 600 with any one of them on.

I took it to Lexus and the service advisor asked me if the AC was on or not when that happened. Apparently Lexus designed the car to run with the AC set to Auto. As long as it is set to Auto you have no problems.

I am not sure though if this is what you are experiencing with your car. I have a 2012 LWB. I used to have a 2008 SWB. I don't remember experiencing this vibration on that car.