Justinsc4

Hi everyone so I have a 1994 sc400 237k miles. I was having alternator issues a while back so I replaced my alternator and it ran fine after that no issues at all. Recently all my interior lights and head lights tails all of it are flashing now whenever the car is running. When it’s off the won’t flash everything is normal. Also it idles kinda rough and if you just let off the brake while it’s in drive without pressing the gas it will start to jerk a little bit instead of smoothly taking off. Haven’t had my battery light come on at all and no problems with it charging. Unplugged the positive terminal while the car was running and it ran fine. Any ideas?

Tallyhoe

Transmission jerk and rough idle can be due to a variety of things... Can be from a damaged ECU to a cracked radiator. I did some troubleshooting on mine, when it was high idle, surge idle, random stalls and no start issues.. ECU was rebuild by Tanin, but it didn't change the surge, transmission jerk. Swapped the radiator cap, it settled a bit, but then went back to the same issue. One thing I noticed was topping off the radiator would stop it all together, but once coolant leaked past a certain point the surge and jerkyness would come back. Replaced my cracked radiator and surge and jerkyness went away. I had evidence of a coolant leak, Engine bay spray and coolant on the ground. I just thought it was the AC or maybe a hose that was leaking since all I was seeing was a large wet stain that went away after a couple hours. These were my issues, yours may just be a damaged ECU, or low on transmission fluid. You may need to do some troubleshooting for yourself.

When you replaced your alternator, did you check your power steering pump to made sure it wasn't leaking? If it's leaking and you have a new alternator, odds are it's causing interference with it, and may damage it. When it's off it's running off the battery therefore most electronics will be stable, unless the battery is dying then you will see things randomly act weird, or die all together. Hope this helps some