JerseyDan

Stan, I'd thought for a long time the torque converter or something with the pump was the issue. I blew up my tranny 3 years ago, and figured it was time to get the question answered. I took it to a shop that was supposed to rebuild it. Holy smokes. They not only butchered my car and left out nuts, bolt, and other goodies, but the tranny has never shifted right since. I took them to court and got some money back. But not enough to go for another rebuild. It still works. It just slams into gear until it warms up. As long as I can keep ol Rex running a while longer, I've thought of getting a lower mileage tranny online and a rebuild converter. But we'll see. Let me know if disconnecting the PS sensor works out.

Good morning Stanley, I'm not sure if you noticed the date of the last post, but this is an old thread. But I'm glad to see someone posting in it ! I bought my RX with 50K on it, back in 08. Two years after I got it, it started having the dreaded vibrating idle issue. I put so much time, effort, and money into trying to eliminate it- but sadly without success. I even wrote a letter to Lexus at some point. I don't remember exactly what their reply was. But they weren't willing to do anything for me. And really, I bought the car already 7 years old. So what could I expect. But the head mechanic at Lexus in Cherry Hill NJ admitted to me that this was a known issue, and there was no known fix for it at the time. This was years ago now, so I'm doubtful anyone has put in the time to solve the issue. But, I'll share with you quickly my thoughts on it. It's still something that annoys me a bit to this day... I bought an bluetooth car scanner that would send data to my phone. And then set it up so that I could watch live data coming from the ECU while I was driving. I was mainly watching the 02 sensor feeds to see if there was some issue with the fuel mix. Like if the car was periodically running rich or lean. I never saw correspondence with that and when the vehicle begin to vibrate at idle. I also changed the motor mounts, and IACV. And numerous other parts in hopes to get rid of the vibration. But here's something I've noticed. The vibration is only an idle issue for me. Sitting still. Typically in Drive. I believe the vibration always goes away if I put the vehicle in park. But I'm not 100% on that. The engine seems to idle properly and smooth when the tach is around 900rpm. But when it drops in rpms to about 600-750 then the vibration begins. Its as if something suddenly loads up on the engine, bringing the speed down and not providing enough power to idle smoothly. Now many systems in the car send a signal to the IACV to up the throttle, when those systems power on. IE - turn your steering wheel a bit, and you'll bring the idle up. The PS pump as a sensor to detect use, and will kick up the idle to compensate. The AC compressor, and headlights do this as well. ... So, question is what is that loads up on the engine, but does not send a signal to up power ? My guess is that it's a tranmission issue. But I don't know enough about transmission function to say that's it for sure. If I ever get to it, I'll figure a way to hardwire one of those systems so that they're always sending a signal to IACV to up idle speed. From my understanding there is no proper way to adjust your idle speed on our vehicles. Anyhow, I need to head in to work. Let me know what you think ? And did I understand this correct ? you're running natural gas in your car ?

Hey Gene, That's a nice looking REX you got there:) I've worked out at three nuke plants in Illinois little ways back. Two were near Morris. I think Dresden and Clinton. And one a good bit south of Bloomington. Lasalle. . You anywhere near those? I think it's great this thread is back a year later :) I just read through it again. We never really came to a conclusion on the cause. But we'd found people on other threads who listed things they did that seemed to solve the problem. The flex connection fix's some Rex's. One woman replaced the Driveshaft support bearings. I had found headlights or other electrical stuff could cause it. We had a theory on Alternator bearings. But one guy seems to rule that out. Someone was talking about PS pump possibly causing it. I've noticed it slightly when i turn my wheel and the pump kicks in. But I'm not so sold on that one. Maybe those other guys will jump back on here and we can take another whack at this. Something I've been thinking about doing is looking into a repgrogammer- to up the idle speed. We had all agreed that it's at a real narrow RPM range that it does it. I think around 750. If we just crank it up a notch it would get rid of it. Wouldn't really be fixing the problem, just hiding it. But, it'd be good enough for me. I think the reprogrammers are a bit pricey. One I looked at the hardware is cheap, but you buy their software specifically for your car. And that cost a bit. Anyone out there interested in splitting this and then we could just mail it around ?

http://s42.photobucket.com/albums/e315/DynoDan83/?action=view&current=file_zpsc7decefd.mp4 video showing the vibration. Just skip ahead to about 1 minute into it. I put my phone on the steering wheel, and then you can really hear the vibration coming through it.

I just realized I have two user names on this forum. NewJerseyDan, and JerseyDan. Ha. Sorry for the confusion folks.

hmm. interesting. I'd guess you're probably just putting enough pressure to stop the vibration. I've never had exhaust work done. But Lexus replaced my transmission at 90K, so they were definitely all up in there. But have never had anything on the exhaust changed. Also, I'd think the downstream sensor would reflect it if the cat was having any problem. :/ No change with the PS belt, either, huh?

Jack, that mileage you're getting is definitely not right. All the maintenance up to date? You should be getting plugs soon. I'd change them now, maybe. Also, cleaning the iacv may hep, as you'd do a lot of idling in city driving. I get 18-24. Probably a little less than half of that is city driving

Holy smokes. Very interesting discovery just now. I'm sitting in my car waiting for an appointment for work. I noticed the vibration was pulsing, like at a very regular beat. I also happen to have my hazards on. Switched them off and the droning reduced significantly. I have noted before that switching my headlights on could start the droning. I'd say this is point to something with the alternator. Maybe it is a failed bearing in there, and it only causes the problem when it's being out under any load. Someone try this out please

Mine is doing the same thing. I'm taking it in today to get oil/tranFluid changed, and I'm gonna have them check that too. I'll let you know what they say