Hey Guys,

my 2016 RX350 has about 100K miles on it. Occasionally at stop lights or when i pull into the garage, the idle gets lumpy.

Any ideas? Note, the car is always serviced with dealer during regular maintenance intervals so i'm not neglecting any regular maintenance.

Not sure if it makes a difference, but every three months i use BG44K fuel injector cleaner.

Please watch this video and let me know your thoughts.

 

During any of your visits to the dealer, did they ever clean out the inside of the throttle body?

 

More knowledgeable folks will have better questions. A few simple questions and thoughts:

• Does the behavior change if you force the AC compressor off? (On my 2020, the AC is enabled in nearly all modes and has to be manually turned off.)
• I noticed a turn signal was on in your video. Does the behavior change if all electrical devices (radio, lights, fan, etc) are turned off/on?
• Is the battery original?
• Lots of other things could come in to play: vacuum leak, dirty injectors, ad nausem
• You could have an auto parts store do a scan with their reader, but if no warning lights are on simple readers might not see any codes.

 

• Does the behavior change if you force the AC compressor off? (On my 2020, the AC is enabled in nearly all modes and has to be manually turned off.) Tried switching AC on/off doesn't make a difference.
• I noticed a turn signal was on in your video. Does the behavior change if all electrical devices (radio, lights, fan, etc) are turned off/on? No electronic devices seems to affect it.
• Is the battery original? On 2nd battery now and was replaced last year.
• Lots of other things could come in to play: vacuum leak, dirty injectors, ad nausem
• You could have an auto parts store do a scan with their reader, but if no warning lights are on simple readers might not see any codes. No warning lights and used the OBD II reader i forgot I had. OBD II reader is showing no codes.

 

I wouldn't particularly use a fuel cleaner in the states. Our fuel in the states comes or is "produced" from three regulated suppliers that have high standards, then companies like kroger, shell, sinclair, etc, will take it and sell it as is or add their secrete sauce as in detergents and anti wear materials. Lexus only recommends using a fuel cleaner every X amount of miles in Hawaii and Alaska

The bg products are really good and potent, but you can run into a lot of issues using them. It is possible that you could have had a decent amount of sediment build up in your fuel filter which could be the additives they add or even the ethanol in the fuel if it sits for a bit. I believe gas only has a 30-45 day "shelf life" in modern cars, its very possible the fuel cleaner broke down this build up into fine enough particles to pas the fuel filter but then clog the injectors.

It does seem the ecu is relearning as a battery was changed, throttle body cleaned, or vacuum leak as bamalam suggested. Maybe unplug the battery for 15 mins and reset the ecu, but your next ~10-20 miles might be rough as it has to relearn. Did you try a new older gas station by any chance? It might have just been a bad tank of gas, gas stations are notorious for never changing out their main filters and when semi's deliever gas they kick up a bunch of sediment in the storage tanks which is never a good thing. I try to never fill up when they get a delivery unless the gas station is newer,

 

I had a milder case of this from the only time I filled up on cheap gas from a place called USA gas.... Ive also seen this before on older cars back in the 90s, MAF sensor?

 

When I owned my 2nd Gen RX I lived in the desert of California. I noticed after a few months the idle would be rough sitting at the light.

I researched the issue and found that cleaning my MAF Sensor would fix the problem.

It’s just two screws to remove.

Start the car, lift the MAF Sensor up just enough to spray cleaner on it.

Then put the sensor back in before the motor stalled out.

Repeat a few times on the Sensor. And also spray into the intake.

It works best if a second person holds the gas pedal down a little while cleaning.

I never did it on my 4th Gen. But it should be the same.

https://m.youtube.com/watch?v=CEKjjXNLTjk

 

Another thing you could try if you have access to a scan tool or know someone who has one. Chart the short and long term fuel trims. If the pattern is not correct, you might have to clean or replace your O2 or A/F sensor. There is a world of information on fuel trim on youtube and other places on the internet. A well equipped technician could also do it for you. It is not all that involved.

 

Seems to be common issue with the V6. Have a look at this thread

https://www.clublexus.com/forums/rx-...ing-issue.html

 

Thank you!

 

I have this same exact problem on my 2016. Next time i'm in for service, will ask for throttle body cleaning and ECU reset.

 

I had my throttle body cleaned during my 110K mile service on my 2016 RX350. Been driven about 100 miles so far and idle has been steady so far....

 

Awesome. Glad I could help.

 

This thread was very helpful. My 2017 RX350 has 83K miles and stopped in Drive with my foot on the brake the engine idle would jump up to 800 then down to 600 a couple of times before landing around 800. I cleaned my throttle body and therefore removed the idling issue. To get to the throttle body is pretty easy, removing the clips for the air filter box and a couple of hoses. I sprayed throttle cleaner on a rag and carefully cleaned the body using my fingers to open the butterfly valve. I have some photos to show the process and result.


Throttle body before cleanup. Mostly carbon on top and bottom edges

Throttle body after cleanup.

Carbon on the rag I used

Idle after startup

Idle after 2 minutes of starting and stopping the car twice. By this time the ECU had been reset.

 

Car Care Nut has a Youtube video on throttle body cleaning, with a caution on how to open the butterfly without damaging the electric motor that controls it.