My 95 sc400 will stall randomly while driving, I will lose throttle response until it coasts to a stop and stalls. Starts back up again and drives fine until it happens again. When I idle it will sometimes stall if I have the AC on and if its off my rpm will be 450 and drop to 250 sometimes. I've already had my ecu rebuilt so I'm thinking either iacv, tps, or fuel pump ecu. I know this is a lot of writing but if you have any ideas about what it could be it would be greatly appreciated, really trying to enjoy this car again. Thank you.

 

I had the exact same issue when I first bought my sc. How old is your battery? Ide check to make sure it isn't going bad since it can cause stalling.

 

I had the same problem with my 92 SC400 and it was the ISC Valve. Here is the troubleshooting information from the 92 Service manual (not sure if it applies exactly to a 95 but it should give you a way to go).

 

I've had this same issue... I've been stalling below 40mph as the RPM just drop like a rock air conditioning on and all.. Last 3 days I've been treating it like a manual where you hold the brake and gas to keep the normal idle, until I stumble and I stall.. Last night I bypassed the Fuel ECU via a jumper wire, and so far its fired right up.. Its only been a day, but I've had hard starts and low RPMs out of the freeway... so maybe a fix..