Sasnuke

I would just clean the throttle body first and see what happens. It's likely a little dirty and the learned value got reset when you swapped the battery...hence the unstable idle.

Solara350

Thanks bro i will do it by Friday or weekend, i don't know anything about electrical is there a DIY ? it eases my headache everytime you reply or i read your post lol

387

If your going out to buy some TB cleaner, pick up a bottle of fuel system cleaner too and dump it in with your next fill up at the gas station.

I did that for the sake of doing it and felt the car drives and idles a lot better now. It could be just in my head though, but at @70k kms I have never experienced what you are. It can only help and is cheap.

jkonquer

The fluctuation between 100 rpm is pretty normal for any cars. Especially during a cold start or an initial start.

you do not need to clean the MAF often unless you are running an aftermarket intake.

Don't sweat it, it sounds pretty normal.

Solara350

Thanks bro, exactly what i wanna describe, car drives normal and pulls fast, the RPM fluctuation between 50-70, i'm just very sensitive person my brother hates me when it comes to car, he said even brand new car isn't running perfect to me.

I did bring to Lexus Dealership, that Cute Asian Service Rep Girl said it's normal. She told me don't waste money for Diagnostic. Anyways thanks for your input.

Solara350

yep i'm gonna change to SHELL gas station this week and dump in a fuel injection in the gas tank, and then look at the TB and MAF, it has to be something with Gas TB MAF Air Filter, thanks bro, i accept all suggestions .

cFoo

2014, it died at 38,000km. I complaint about the rough idles a year earlier during cold weather but they kept saying it's normal until the car warms up. It finally died this winter, smack in the middle of a snow storm. All 3 injectors went out on one side of the engine. At first they threatened I would have to pay for it if they open it up and it's a rat chewing the cable. After a week they finally got the parts in to replaced it. Anyway, full story https://www.clublexus.com/forums/is-3rd-gen-2014-present/842845-fuel-injectors-dead-350-awd.html

cFoo

Never. I gas at the same Shell station for the last 10+ years of owning multiple cars. No ethanol added for Shell 91. I also gas the family SUV at the same station so if it's bad gas surely the turbo charged engine would have been gone by now. I can't think of anything else other than bad luck with Lexus parts.

I've also taken the car south twice the first year and gas only at Costco.

Solara350

yep just filed up gas at SHELL right at Richmond Hill Time Square, car drives better but RPM dipping still there.

Sasnuke

You can look for some videos on Youtube to see how to clean the throttle body on a variety of vehicles. Unfortunately I didn't see one for the Lexus IS.
The process realistically is the same:
1. Remove intake tube from throttle body
2. Spray the intake cleaner/throttle body cleaner (that you can purchase at Canadian Tire) around the throttle flap first
3. Using a rag, spray some cleaner on the rag
4. Hold the throttle flap open with one hand while wiping around the bore and flap until all the carbon is removed

You can spray more cleaner as needed around the flap to clean as necessary.

Once you reassemble the intake tube, the first start may be rough.
The engine may shake a bit, it may even stall, and you may see odd colored smoke coming out the exhaust...not to worry, this is normal.
Let the vehicle idle until the smoke clears and shaking stops. Take the car for a drive to burn off any remaining cleaner in the engine.

Solara350

thank you bro, ill probably do it on sunday. i still doing research about this ill post video tomorrow, this minor dipping also same as GS350 Fsport and Lexus LFA some LFA even worst than mine along with other IS350 Fsport. I gotta wait for a friend to come back from vacation to clarify if this is normal, i don't have Trust in Dealership. Ill try to do Throttle next before he's back, just switch to SHELL gas car drives even better but dipping still there.