I have what seems to be a misfire in my 95 sc300, I just don’t know what could be causing it. It started when I gave it some juice at 50 mph and when it shifted it started to heavily sputter and misfire. It calms down with less misfire after i turned the car off and back on but once i get around the same threshold it goes back to very heavy sputter and misfires.

I believe everything is stock except the spark plugs. Car has 169,000 miles on it. I just don’t even know where to start please help

 

Weird conditions occur when the ECU capacitors begin leaking onto the PC board traces. If you do not know the exact tested condition of your ECU, highly recommended you remove it and get it tested/inspected and afterwards restored/repaired/certified if needed.

When the ECU has a “clean bill of health”, then proceed troubleshooting from that point forward.

https://www.clublexus.com/forums/per...s-by-year.html

I suggest SIA to perform that service. Takes about a week..

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

 

When was the last time the valve cover gaskets or spark plugs were done?

When I opened up my 95 SC300 after a misfire, i found the spark plug galley filled with oil to the top of the spark plugs from a valve cover leak never fixed. This is some-times hard to see because one, the galley has a cover over it and two, the throttle body crosses overtop the valve covers and needs to be taken off to do the job properly.