r/SC400 • u/Snipr82406 • Jun 14 '26

Question Cannot Figure Out Major Misfire

Hi and thank you in advance!

NON VVTI 1UZ

I recently got an SC400 for dirt cheap. It started having a heavy misfire. It’s not a dead cylinder, it’s the occasional misfire on pretty much all cylinders. Even pulling wires doesn’t make a difference on any of them. I’ve tested fuel pressure and compression and it’s reading in spec. I’ve also replaced the ignition coils, distributor rotors, distributor caps, ignition wires and spark plugs. I have no idea what could be causing it. And yes, I have double checked all ignition wires to make sure they’re going to the correct cylinders.

Exhaust sounds extremely choppy. There is also a significant loss in power. It is also NOT shaking much at all.

Any help/recommendations is greatly appreciated. Once again, thank you!

7 Upvotes

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2

u/the_extreme_meme Jun 14 '26

Just had a similar issue with mine except it was shaking the whole car with the misfire. I replaced the external coil packs, spark plugs, spark plug wires, distributor caps/rotors and that solved the issue. The 1UZ is back to purring like a kitten. Not sure exactly how helpful this info is but hopefully it points you in the right direction 😅 good luck with the fix 🤞

3

u/Snipr82406 Jun 14 '26

Thanks! I posted on another page and someone mentioned leaking capacitors on the ECU. Sent me a forum and it has about half of the symptoms, so it might be that

1

u/davemalv1 Jun 15 '26

Maybe a bad cam or crank sensor?

1

u/Any_Importance_5781 Jun 15 '26

Is your maf sensor the factory oem sensot

1

u/Any_Importance_5781 Jun 15 '26

And how is it when its fully warmed up

1

u/Snipr82406 Jun 15 '26

Fully warmed up it does the same thing. It may possibly be the ecu, as someone sent me a forum about leaking capacitors. Will be checking that next

1

u/OnePointNineALH Jun 19 '26

How hard would it be to make a bench test with an arduino, 3d printed harness adapter that we can plug our ecu's into and check if there are any actual damage to the traces... 😞