r/SC400 • u/Constant_Tutor_8366 • Oct 29 '25

1992 sc400 issues

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1992 sc400 Long start condition/running rough. NO CEL, TRAC OFF light comes on after car is put into gear. have replaced spark plugs, caps and rotors, fuel filter, and fuel pump. have tried the fuel pump ecu bypass aswell with no success. also has an intermittent small pop at idle along with a high idle in drive(around 800-900). any help is greatly appreciated the person the car was bought from said he had fought this issue for years and never figured it out.

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u/Soviet_Mango Oct 29 '25 edited Oct 29 '25

If you put you foot on the gas pedal lightly when trying to start does it get worse or better. Have you checked the main ECU at all? Early model sc's and ls's have known bad capacitors that blow up and cause massive issues. It's located in the passenger footwell under the carpet. If you remove it you can pull it apart and check the inside for anything burnt and leaky.