RnmGs

First off, Hello ClubLexus members, I'm new to this site and came here seeking help from fellow gs300/is300 owners.

I, Myself own a 2003 Lexus Gs300, (Auto Tranny) which I bought for $1000. 165k Miles, Engine runs great, interior/exterior in pristine condition. Got a pretty good deal on her!

Except, for one small issue. I feel like the car is holding back a lot of power, and not running to its full potential. I'm pretty sure it's not the engine, but I think it might be the transmission.
The transmission shifts through all the gears, but I have to let off of the gas whenever I feel like it's time to shift, and that's when it shifts. Almost like I'm driving a manual transmission, except it doesn't have a clutch, or way to actually shift the car manually. Does anyone have any thoughts or anything from previous experience, or some common issues the Toyota a650e has when it comes to power loss?

Things I have done so far that kinda helped a bit/didn't really fix the main issue

- Clean MAF Sensor (Was quite a bit dirty actually, helped just a little bit)
- There was a massive crack on the airbox, after the MAF sensor, which was letting in Un-Metered air, which isn't good.
(JB Welded it, and fixed the acceleration just a little bit when shifting from 1st to 2nd)

Basically, I've exhausted my knowledge of what's wrong with the car.
I will post a video soon on me accelerating it, and how weirdly it shifts.

Any insight on what it could be would be awesome! Thanks.

TrueGS300

Ive seen this kind of thing in older vehicles with kick-down cables. Have you tried cleaning out your throttle yet? Try that and reset the computer by disconnecting the battery cables and holding the cables together to completely drain the systems memory. It will need reset to run right after the throttle is cleaned. I think its throttle related because when it happens to the vehicles I'm talking about, it in essence thinks that it is seeing wide open throttle all the time. With kick-down cables it can be adjusted manually, but with an electronic throttle, it's either position sensor adjustment, or simply operating poorly due to carbon build up. I find it best to remove the throttle to get the back side and blade clean enough. I'd try that and let us know if there is a change. It's free and might just fix the issue. And there are many other benefits to a clean throttle including restored power, throttle response, and fuel economy, plus smoother idle. The throttle has a great deal to do with how a transmission shifts. So it's a good place to start.

Gs300maste

When I had a vacuum leak through old pcv valve I had a shifting issues like yours. I couldn't find any vacuum leaks from lines at all in engine bay. When I replaced pcv valve with new OEM one my shifting problem went away. Car got a lot of power back also. Check and see your ATF level too. I got mine at the extract MAX reading line when its hot eveytime.(lots of tests and errors I had to drain a small amount and pour some in btw 15-20 driving each times to get there probably an over kill since hot fluid level only needs to sit btw HOT low and high lines).

2013FSport

iTrader: (2)

Good advice above. Sounds like it has a vacuum leak still. While cleaning TB look at all of the lines and verify none cracked or routed.
Have you looked at the fluid condition? Not likely to fix this but you might dump it and put a new filter in there.