Hey everyone,
I have been gone from the forum for a while but I'm back with a question. I have a 2010 460 with about 125k miles. For roughly the last 2 years, I've had a rough idle but I've just dealt with it - the time has come for me to address it and I need some feedback. Here's the situation:

• Rough idle in drive, but it's not consistently bad. On "cold" mornings (in FL), right upon start is when it's the worst for about 5 minutes while the engine heats up. It's pretty bad - I can feel the vibration in the steering wheel and if I have anything in the cup holders they'll make noise from the vibration all through the car.
• It's completely silent and still when in neutral. Reverse has a bit of rough idle, not as bad as Drive, but not as silent as Neutral.
• I moved out of town and no longer have my trusted mechanic, but I have found an indy Lexus/Toyota specialist shop that I like so far. They did a VERY thorough inspection of my car, took a ton of pictures, and made some recommendations on things to do in general.
• 2 years ago when I had my interior replaced through the ZLZ program I brought up the rough idle to my Lexus dealership (which I never trusted and never took car there for anything other than warranty work) and they gave me a $3,300 quote for replacing the engine mounts. It's no surprise to me that they quoted the most expensive thing as that's par for the course for this dealer.
• My new local Toyota/Lexus indy shop did not notice any wear on the engine mounts 4 weeks ago during oil change
• I bought my car about 5 years ago with 65k miles. I looked at the service history before purchasing but somehow overlooked that spark plugs were never done...and I've never done them. Could this be my culprit? 125K miles on the original plugs seems quite excessive. Since this has been going on about 2 years, it started around 100k miles.

My main confusion is around the fact that there is no consistent level of the rough idle. Some days it's really bad, other days it's tolerable (but noticeable to me as I've owned 3 LS's so I know what to expect). I also don't know if/how engine mounts can be visually inspected to be sure they aren't the issue.

What thoughts do you guys have? I'm taking the LS to the new shop in about 10 days to get them to drive it and give me their input. Nonetheless I'm going to replace the spark plugs - what are the odds that fixes the issue? With a 12 year old car, I really don't know if I'd spend $2,500 or so at this point to replace engine mounts - I'd probably just get something else. I just want my LS to drive like an LS again so I need your insight and recommendations. Thank you!

 

Nice to see you back. I believe that year recommends 50k on plugs. Even the newer models are at 100k. First, get some MAF cleaner spray and clean both sensors, it also works well for the throttle body and butterfly. All can get a bit gummed up and will affect idle. All are likely to be dirty at your mileage. This is a cheap and easy try to smooth the idle. It may take a few days of driving for the computer to adjust to the cleaned items. Both are easy DIY. Also run a can of fuel system cleaner in tank and floor it on the highway.
While it's unlikely your mounts are totally shot (based on conflicting inspections), there's a video on you tube showing how much our engine moves on the motor mounts when revved. Compare that to how much your engine moves. Not definitive but might be visible if the mounts are shot.
The price of used cars are so high right now. I hope some simple maintenance does the trick for you.

 

My car (2007 SWB) had very similar symptoms to what you are experiencing jrmckinley and the solution for me was replacing the engine mounts. Mine has been smooth as silk since I did the replacements almost a year ago now. I did mine DIY so I wasn't up against a $2,500 shop cost and I believe I spent about $250 for the front engine mounts. I also replaced the rear engine/transmission mount at the same time and that was another $120 for the part. Good luck. There is a good thread on here if you want to consider the DIY route. BTW my engine mounts had 157K miles on them and looked perfect with no obvious signs of wear before replacement, but upon removal you could tell they were shot.

 

Interesting, thank you - I'm not much of a DIY type but both of these sound easy enough (and low risk) that I can give them a shot. I'll check out the YouTube video also, hadn't thought of that. And I believe on my model year spark plugs are recommended at 60k. So I should've had them replaced at 60k...and potentially again at 120k...whoops!

 

Interesting, thank you. Was your rough idle consistently rough or was there some variation? I am struggling to understand why bad engine mounts would lead to variability in how rough the car is idling while in Drive.

 

Well, even in drive, the car RPM goes up and down....

 

I'm not understanding your response. My RPM's aren't fluctuating - but there is a lot of vibration and noise within the cabin while I'm in "D" but at a complete stop. I've been an LS owner (400, 430 and 460) for the last 14 years - one of the LS defining signatures is how it's eerily quiet when stopped. This is far from it, so I know something is wrong. I am just hoping it's not the engine mounts given how expensive (labor intense) that is. It will create a dilemma on if I want to put that much into a 12 year old car, and I really don't want to get rid of it.

 

Do you also have vibrations when driving , let's say, at 70 ?

 

Engine mounts

 

Once the mounts were bad, I consistently had vibrations at idle while in drive, but the vibrations did vary in intensity depending on whether it was right after start up or if I had been driving for a while. The vibrations also would change depending on whether I had the A/C on or off and at different fan speeds. There are a variety of operating conditions that can slightly vary your RPMs at idle and that translates to different vibrations. Once I pressed the accelerator and was no longer at idle the vibrations always went away. I hope this is helpful.

 

Does the rpm go down when you put it into D?

 

Hi RPM, less vibrations....check your mounts....

 

Mounts make sense now. Idling, there's no torque from the engine, so it bounces around on the bad mounts. As rpms increase in gear, the torque makes the engine steady/firm against mounts on one side. This is my theory of reverse engineering. I could be all wrong.
While you may not want to invest more money in the car, I'll bet there are buyers out there would love to have it!

 

Unfortunately I agree, it's your mounts. On my 07 460 when my mounts were going out the vibrations when cold were the worst. Once the car was hot vibrations were less noticeable. Initially it was just the interior vibrations as you described. After a few months my fender started to resonate from the vibrations. Made for some super proud moments at stop lights.

The rubber part of the mount is enclosed by metal, there is no way to visually inspect the vibration dampening part of the mounts when they are installed. About 10k miles before I purchased it the previous owner had brought it in for vibrations. A lexus dealer diagnosed the mounts as fine. . I bought the car and drove it for 6 months or so before replacing the mounts. It has been smooth ever since.

 

This is what they look like. If a shop were to try the typical method of checking the mounts ( foot on brake in drive / reverse and push accelerator pedal) it may damage the mounts even further.