Sc400 loss of power, runs rich, loud - ClubLexus - Lexus Forum Discussion

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Sc400 loss of power, runs rich, loud


Old 05-15-18, 08:21 PM
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Default Sc400 loss of power, runs rich, loud

Sorry if this is in the wrong area, but please take it easy as Iím new to the site.
I recently bought a 92 sc400 and it ran perfect for about 2 weeks before randomly messing up one morning when I tried to start it.
Before any major issues, the car randomly stalled at stop lights every once in a while.
Barely wanted to start, cranked and cranked until just barely starting up.
Next, I tried driving down my street and it kind of bogs down when I floor it, but will get up to speed when I slowly accelerate. Drove it around fine, up to 50 mph but like a slug.

Before problems started, previous owner replaced plugs, coils, valve cover gaskets
BFI Intake mod
Has a straight pipe with resonator, no cats
It also has a ďbypassedĒ fuel pump ecu, seller told me it acted funky before he installed a switch to manually turn on/ off the pump. Acts weird, turns off with car sometimes, other times fuel pump will keep running forever with the car off.
I also tried replacing an ignition coil which had a hole burnt in the side, runs a bit better but not perfect. Might try replacing the other one.

Other than that, Iíve pulled all driver side spark plugs, some are a bit burnt but not covered in oil or anything. Iíve also checked the throttle body, itís pretty clean and snaps perfect, opens all the way when floored in accessory mode. After sitting in my garage a few weeks,and turned on a few times it also started misfiring pretty bad when revved up. Sounds like 2 step.
Any help with this would be greatly appreciated, as Iíve taken it to 2 shops with little to no help. First shop said transmission or computer, second shop told me to rewire the fuel pump back to the computer.

Last edited by Braaap1uz; 05-15-18 at 08:37 PM.
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