Rough Idle When In Gear

[lenore]

The vibration sensation can also be the flex pipe on the exhaust just under the engine area....

[JerseyDan]

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 ?

[SHUMIF1]

I read that lexus knew about the vibration but didn't do anything about it, it comes from the resonator in the exhaust.

[NJerseyDan]

There was like a small weight attached to my exhaust attached with a rusted out tab. Busted off on me years ago. Would that have been a resonator?

[UCF3]

Resonators are generally holly metal canisters. All exhaust pipes are expected to rust out especially when someone lives in the snow belts. is it possible there are some loose or saggy rubber hangers that need to be swapped out for new one?

[GeneG2014]

I thank all of you guys for your replies. Yeah, exhaust is gonna be the first thing I'm gonna look at when it gets a little warmer ouside. I'm having 2 small leaks from my exhaust in 2 different spots. There are just too many theories out there about this vibration issue, and I guess I'll have to isolate them one by one. There's also a small shock absorber underneath the engine area(there may be even 2 of them), did anyone try to replace it ?

[SHUMIF1]

The resonator is the muffler looking thing befor the muffler itself. some call it resonator and some intermediate pipe. NJerseyDan... there is a weight on the front of that that could of rusted.

[SHUMIF1]

I wonder If anyone who ever put an aftermarket exhaust on has this vibration ?

[GeneG2014]

This is exactly where the smoke leaks from in my case. A muffler-looking, but much smaller thing, just pass the front axle....

[GeneG2014]

My average is 16 mpg during the summer time and 14 mpg during the winter time, when I have to idle to warm it up a little. I use 89th gasoline all the time and I mostly drive it in the city. The computer is showing an average speed of 17 mph. So basically I'm having the proportion of 14 mpg/17 mph. Anyone wants to post their's ? It seems a little low to me...

[stanleybg]

I have the same problem , but i think the sound is because of low idle.I changed all 4 engine mounts , and IAC valve with brand new OEM and no any difference at all.I think the exhaust could be the problem.All intake gaskets i changed them with new OEM ones and nothing.MAF readings are 3mg wich i think is normal.What MAF readings you have on warm and idle ? I have LPG system installed and it is doing this on both fuels.That means not an injector issue.

[JerseyDan]

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 ? 

[stanleybg]

Yes i saw it was long time ago 🙂 

I think torque converter is not properly working and it is loading the engine too much.The only think that i did not touch was the converter it self.I should send it to be remanifactured or replaced.may be i will wait until it starts making sound or some problems and then will do the converter.Or the easyest way is to modifi steering sensor to high up rpms.I think if disconect it it will keep rpms high.On other  car i did this and it works.

 

 

[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. 

 

[stanleybg]

Valvebody need to be changed with new one.Or with sonax full upgrades one.I changed it.No it is changing very good , but i rebuild all the transmission with this.Without touching the converter.All rebuild i have done is with OEM parts.About 4000$.I rebuild it by myself.With amsoil , two sensors and all transmission cables are changed with new OEM.Every !Removed! thing :). But still when i release the gas pedal and then press it it slams a little especialy on hot engine and tranny.I think somethink in converter is bad.