I have a 1996 lexus ls400 with 240xxx and I am a new owner. I bought the car and it ran fine for about two weeks then one day after stopping at the store I went to start the car and it started but was surging really bad as if I was mashing the gas pedal on and off in park. I had to get home so I went to put it in drive and it wanted to go. No foot on the gas at all and the car went 40mph down the road! I was driving with the brakes at this point. The next morning the car started fine, I thought it was strange and did some research about ls400 acting up like this and basically came to the conclusion that my capacitors in my ECU had gone bad and leaked out on to the circuit board. Unsure about that being the actual cause of my problems I drove the car for about a week more and the problem got to the point where I could only start it in the morning once, any time after that it would start in its surging mode. Finally I ordered capacitors off of digikey and took the glovebox out to get to the ECU. I took it apart and sure enough some of my capacitors were corroded. I replaced them and reinstalled the ECU and the car hasn't given me any problems so far and it seems to run better, it almost woke the car up. (First pic old capacitors) (second and third pic bad capacitors) (forth pic new capacitors installed)

 

Thanks for reporting the successful repair. Glad the trace on that one really ad leak was still good.