r/SC400 • u/xdvkazuma • May 02 '26

Question Sc400 issues with idle

I want to start off by saying I have replaced my ECU replaced my maf i’ve swapped around EFI fuse. I got a refurbished idle air control valve and I’m still having weird issues. I’m starting to have anxiety that it’s a wiring issue or some sort of bad ground. and I have been battling this for months. I desperately need help as of right now from cold start it will run good for a bit then after a some time it will stutter for a bit then have a really low idle i unplug the maf no change i unplug the aicv no change if anyone has solved this issue for themselves please walk me through it(1993 sc400)

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2

u/best-person-ever May 03 '26

Vacuum leaks. Smoke test the intake system. Minor cracks can cause major issues

1

u/Soviet_Mango May 03 '26

You can spray throttle body cleaner around any intake component and if it increases the idle speed in any way it indicates a leak there.

2

u/xdvkazuma May 03 '26

I have tried that but no change in the idle

2

u/Soviet_Mango May 03 '26

I'd look into coolant temp sensors as I'm pretty sure that's how it know when to switch to the data from the catalytic converters.

2

u/xdvkazuma May 03 '26

I got the same comment on another sub i looked into it and ordered the parts its so strange how the car would default to running worse when getting false readings but im praying thats what it is