Beastman

Any help would be so helpful. I'm experiencing vibration /humm resignation throughout the cabin, when....
AC on, in drive, foot on brake. When AC comes on and stays on the cabin has a very noticeable resignation vibrating Humm. I put car in park or neutral it goes away. When noise happens rpm's jump from 500 rpm to 700 and then fluctuates a bit. LEXUS DEALER has tried new plugs, hand cleaned throttle body, cleaned fuel injectors, depleted AC freon and then refilled. They pulled intake, Checked all hoses and put in another set of plugs, new mass air flow sensor as well. Lexus say AC compressor is good, they also Che ked motor mount and said there is such little wear it's not the cause. Mechanic also says he's never seen motormounts go bad on a 460. 3 mechanics and lead diagnoser have no idea what it is. All I know is that it's not normal and very irritating. GX is from WI with underbody rust and all maintenance has been done.
It did have a somewhat rough idle when I bought it @ 94,000 miles, but AC didn't do what it's doing now.
Lexus has given up, which I don't find acceptable with having an obvious issue.
Bright side is they didn't charge me a dime after 8 days in shop and a few hundred in parts. Lexus of Clearwater by Autonation gets a thumbs up except for not figuring out my issue.
Feel free to call, I'm supossed to pick up tomorrow. 970 875 4269.
I really need help!
Bill
( beastman) is my user name
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Margate330

Hi Beastman,

Ok, I went thru something like this that drove me insane and I almost traded the car in just to be done with it.

Lots of info so bare with me.

I had the same vibration only at idle and it was worse when running the AC.
The car was a 2004 RX330 with 150k miles and was throwing no codes.

Since it wasn't throwing codes I knew if I took it to the shop they would either not spend the time to properly diagnose it -OR- throw the kitchen sink at it and
recommend thousands of dollars$$$ in replacement parts hoping for a fix.

Reason I knew this is because I turned some wrenches as a very young man when I was right out of high school and saw this on a daily base for 3 different shops I worked at.

I did some basic testing and replaced all my O2 & A/F sensors that were either slow acting or looked flaky on the live data- no change.
Also, I replaced the MAF because it was a little "under reporting", almost no change but felt like may a very little, was hard to say but that wasn't "it".

So... I took it to a local shop who had excellent reviews and asked to pay for diagnostics -however long it takes- to figure it out and fix this.
I waited in the lobby and after about an hour the manager walks up to me and says the car runs great and don't bring it back until it's throwing codes.

DUH... lolol I knew that's what they would say but it runs like crapola and misfiring so bad it's shaking my dashboard.

Over the next month I kept a scanner plugged in and monitored my fuel trims which were running at approx +8-9 for combined long term + short term- while idling and engine up to temp.
I did mention the elevated fuel trims to the mechanic shop but they just hand waved me away saying that was within normal range- yeah, maybe so but there is an issue and I disagreed with their diagnosis.

Anyway, after a month of watching my scanner while driving and idling at the traffic lights I would notice every once in a while the fuel trims would improve and engine would smooth out at idle- only for a short time but it did.

Next I pulled the dash board and pinned the wires at the ECM and hooked up an oscilloscope and scoped all the sensors- crankshaft, camshafts, knock sensors, ignition timing, etc and everything looked excellent.

What the hell?
Then I reached my hand behind the intake and while cutting and scraping my hands trying to get back in there I wiggled the coil connectors and heard a change in idle and a small improvement so I changed all my connectors.

Next I pulled all the plugs looking at the carbon deposits for any clues that I have a bad cylinder but all the plugs looked equally worn so that wasn't it- but replaced them all again anyway.

Out of desperation and process of elimination I had a theory that whatever the issue, it was affecting all the cylinders approximately equally- fuel trims +8-9% both banks,
spark plugs equally worn, sensor signals looking good, etc.

So next I wondered, "Do I have weak spark?".
I ordered new ignition coils and WHAM BAM THANK YOU MA'AM, massive improvement.

My coils were only approx 3 years old and bought online but I believe they were Denso clones that worked well when new but quickly degraded over time causing a nightmare for me but I can see this happening naturally with oem original coils too when the mileage gets high.

My fuel trims were now back to normal and vibration was almost gone.
Next I did a Seafoam oil treatment- dumped in the whole bottle and drove 50 miles and did an oil change- more improvement.
Next I did a Seafoam intake treatment- more improvement.

I believe your mechanic was on the right track because they went for the spark plugs and the throttle body cleaning.
On my car it took all that plus new ignition coils, new coil plugs, and some Seafom treatments- it was a combo of things making the perfect storm. lol

Good luck and let us know how it goes.

Blaze876

iTrader: (1)

Does the vibration happen as soon as you turn on the ac and never goes away unless you turn off the ac? Or does it happen on and off while the ac is on?

Beastman

The droning Humm only happens when AC is on, but will go away when put in neutral from drive. But also goes away when the compressor kicks off. Today the entire seat was vibrating worse than any droning noises, something is getting worse.

Then also today I'm told my timing cover gasket has failed. Same thing on my 2011 GX and now the 2016 with 121000 miles. I'm about to give up on owning anymore Lexi they seem no better than any other car.