99 sc400 137k. I have only put about 1500 miles on this car bought from original owner that always had it serviced at lexus. They did a good job of keeping all receipts

Car mostly sat the last 4 years until I purchased it

Twice recently it seems it doesn't come out of gear at a stop light and lunges

Fluid level seems right

 

Have fluids been changed since it sat for 4 years or only filled up to their proper level? Old fluids that have sat for that long can be gunking things up.

 

I did not see any receipts for a transmission service.

I have been reading a little about that, wgats the proper way on a car that age that has been sitting. I know it takes T IV fluid

 

ECU likely has leaking capacitors and broken circuit traces. Best to inspect/ repair before going down a lot of rabbit holes….

 

What's the best method for this? Remove it and send it out?
This car is in very good condition

 

Depends on your budget and tolerance of down time. Buying a spare (hopefully tested/rebuilt) can be $500-700 or more.

Removing it and sending it out for testing/repair can be around $200 but will be 7-10 days turnaround.

I used SIA for this service. Others have used Tanin.

https://siaelec.com/product/lexus-sc...repair-return/

 

That radiator looks to be on its way out, so don't assume all the maintenance is up to date.

Leaking capacitors in the ECU was my first thought, too. Maybe bad shift solenoids or a clogged filter. I'd be surprised if old fluids can cause that issue, but you never know.