Hello, I've really been enjoying my 99 gs300, but I have a few questions. When I'm sitting at a stoplight or stop sign and I give it gas if I don't feather the throttle, it sorta jerks right when it starts to move. I've read that it's just a thing these cars do. It doesn't feel right though. It isn't a shifting problem, the transmission shifts really smooth.

Also, when I first bought the car. If I was going down a hill and tapped the brakes it would automatically downshift and engine brake. It doesn't do that any more. I liked the feature and am curious how I could get it back.

Overall it runs, drives and shifts great! I'm definitely going to be owning it for a looong time. Thanks for the input i really appreciate the help!

 

I had this issue with my gs @ 170k miles
my rear diff gave because of my lack of maintenance. Check your rear diff fluid and if it’s silver (mine was VERY silver- 0% translucent) replace that rear diff or rebuild it

 

A lot of what you're mentioning has to do with throttle position. It is likely gunked up w/ oil and carbon. Scrub it out and reset the computer to clear the learned values and start fresh. Do this by disconnecting the battery for around an hour, or overnight, or sometime you won't be needing it for a few hours. If you don't, the computer will retain the learned values of the choked airflow and you'll have a difficult time with rpms and shifts. The computer is capable of adjusting many parameters as a throttle gradually gets dirty (typically a 100k service) but a major sudden change (like cleaning it out) will register as a failure and throw an engine light and runability problems. So all you have to do is reset the computer after cleaning it out.

 

This. Much more likely to be throttle position than rear diff, but it also never hurts to replace your rear diff fluid jus for the sake of doing it.
Berryman's carb cleaner is my personal favorite for cleaning throttle bodies - Just make sure it's not going anywhere except the butterfly valve.
Clean out the sensor socket and clip with mass airflow sensor cleaner, especially if you suspect any carb cleaner splashed onto it.

 

check and clean mass airflow sensor
check and clean throttle body, especially the plate whether its moving freely or gunk around the edges
check tps, throttle position sensor, youll need a multi meter to check and calibrate if need be.

those are the easiest things to check first, well at least the first 2. you can pick up some maf sensor cleaner, and it will work on the throttle plate as well.

may need to reset ecu by disconnecting neg on battery for 15-30mins, we would do a throttle body service at toyota sometimes and the ecu was so use to the adjusted values for the dirty throttle body that it would not hold idle.

 

Thanks for the reply. I have since repaired the issue. It was a dirty intake flap, and the resonator box had a big crack along the seam of the bottom going almost all the way around it, it was sucking in alot of unmetered air. The previous owners had also installed the air filter wrong so it was sucking in alot of unfiltered air. After giving everything a good clean, a seafoam spray treatment, and resealing the resonator it no longer jerks. It idles, drives and shifts smooth as glass now. Now I i think it needs a wheel speed sensor because the abs, vsc, and vsc off lights are on. It also won't engine brake when I press the brakes, i miss that feature alot!

 

Those are boxes ALWAYS FAIL. If you haven't replaced yet you are bypassing the MAF.